Centrifuge System for Separating Cells in Suspension

ABSTRACT

An apparatus for separating cell suspension material into centrate and concentrate, includes a single use structure (178, 240, 250, 370, 414) releasably positioned in a cavity in a solid wall rotatable centrifuge bowl (172). The bowl and portions of single use structure rotate about an axis (174, 428). A stationary inlet feed tube (184, 430), a centrate discharge tube (212, 436) and a concentrate discharge tube (230,448) extend along the axis of the rotating single use structure. A centrate centripetal pump (208, 438) is in fluid connection with the centrate discharge tube. A concentrate centripetal pump (216, 450) is in fluid connection with the concentrate discharge tube. At least one concentrate channel (380, 454) and a concentrate centripetal pump chamber (376,452) have configurations in the structure that facilitate the flow of cell concentrate.

TECHNICAL FIELD

This disclosure relates to centrifugal processing of materials.Exemplary arrangements relate to devices for separating cells insuspension through centrifugal processing.

BACKGROUND

Devices and methods for centrifugal separation of cells in suspensionare useful in many technological environments. Such devices and methodsmay benefit from improvements.

SUMMARY

The exemplary arrangements described herein include apparatus andmethods for centrifugal separation of cells in large-scale cell culturewith a high cell concentration using pre-sterilized, single-use fluidpath components. The exemplary centrifuges discussed herein may be solidwall centrifuges that use pre-sterilized, single-use components, and maybe capable of processing cell suspensions, with high cellconcentrations.

The exemplary arrangements use rotationally fixed feed and dischargecomponents. Single use components often include a flexible membranemounted on a rigid frame including a core with an enlarged diameter. Thesingle use components may further include at least one centripetal pump.The single use structures may be supported within a multiple use rigidbowl having an internal truncated cone shape. These structures permitthe exemplary systems to maintain a sufficiently high angular velocityto create a settling velocity suited to efficiently processing highlyconcentrated cell culture streams. Features which minimize feedturbidity, and others which permit the continuous or semi-continuousdischarge of cell concentrate, increase the overall production rate overthe rate which can be achieved. Exemplary structures and methods providefor effective operation and reduce risks of contamination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary arrangement of a centrifugesystem including single use and multiple use components.

FIG. 2 is a close-up view of the upper flange area of the centrifuge ofFIG. 1, which shows a method of sealing the flexible chamber material tothe surface of the flange.

FIG. 3 is an isometric cutaway view of the core and upper flanges of thesingle use component of the arrangement the centrifuge system of FIG. 1.

FIG. 4 is a schematic view of the arrangement illustrated in FIG. 1, inwhich the pump chamber of the centrifuge system includes acceleratorfins.

FIG. 5 is an isometric view of the top of the pump chamber of theexample arrangement of the centrifuge system illustrated in FIG. 4.

FIG. 6 is an isometric cutaway view of the core, upper flanges and lowerflanges, of a single use centrifuge system with an enlarged corediameter (to create a shallow pool centrifuge), and a feed accelerator.

FIG. 7 is an isometric view of the feed accelerator of FIG. 6.

FIG. 8 is an isometric cutaway view of the core and upper flanges of asingle use centrifuge system with a standard core diameter, and a feedaccelerator with curved vanes and an elliptical bowl.

FIG. 9 is an isometric view of the feed accelerator of FIG. 8.

FIG. 10 is a schematic view of a portion of a continuous concentratedischarge centrifuge system.

FIG. 11 is a schematic view of a portion of another arrangement whichincludes a continuous concentrate discharge centrifuge system.

FIG. 12 is a schematic view of a continuous concentrate dischargecentrifuge system with diluent injection.

FIG. 13 is schematic view of a portion of a further example arrangementof a continuous concentrate discharge system, with a throttle mechanismfor the centripetal pumps.

FIG. 14 is an isometric cutaway view of the core and upper flanges of asingle use centrifuge system with a core, and a feed accelerator withstraight vanes.

FIG. 15 is an isometric view of the feed accelerator of FIG. 14.

FIG. 16 is an isometric cutaway view of an alternative continuousconcentrate discharge centrifuge system.

FIG. 17 is an isometric exploded view of an alternative centripetalpump.

FIG. 18 is an isometric view of a plate of the alternative centripetalpump including the volute passages therein.

FIG. 19 is a schematic view of a centrifuge system which operates toassure that positive pressure is maintained in the centrifuge corecavity.

FIG. 20 is a schematic view showing simplified exemplary logic flowexecuted by at least one control circuit of the system shown in FIG. 19.

FIG. 21 is a cross-sectional schematic view of an alternative continuouscentrate and concentrate discharge centrifuge system.

FIG. 22 is a cross-sectional schematic view of a further alternativecontinuous centrate and concentrate discharge centrifuge system.

FIG. 23 is a cross-sectional schematic view of a further alternativecontinuous centrate and concentrate discharge centrifuge system.

FIG. 24 is a schematic view of the control system for an exemplarycontinuous centrate and concentrate discharge centrifuge system.

FIG. 25 is a schematic representation of logic flow associated with anexemplary control system of FIG. 24.

FIG. 26 is a cross-sectional view of an exemplary upper portion of asingle use centrifuge structure that includes concentrate and centratedams in the separation chamber.

FIG. 27 is a cross-sectional view of an exemplary upper portion of asingle use structure that includes vanes in the centrate pump chamberand the concentrate pump chamber for purposes of controlling the radialposition of the air/liquid interface.

FIG. 28 is a perspective view of a chamber surface of an exemplaryconcentrate or centrate pump chamber and that includes a plurality ofchamber vanes.

FIG. 29 is an axial cross-sectional view of an exemplary upper portionof a single use structure similar to that shown in FIG. 27 showing aposition of an air/liquid interface.

FIG. 30 is an axial cross-sectional view of an exemplary upper portionof a single use structure including an air passage for maintainingpressurized air in the air pocket.

FIG. 31 is a schematic view of an exemplary system for controlling acentrifuge system including centrate flow back pressure control.

FIG. 32 is an axial cross-sectional schematic view of a furtheralternative continuous centrate and concentrate discharge centrifugesystem.

FIG. 33 is a cross-sectional view of the upper portion of the systemshown in FIG. 32.

FIG. 34 is a cross-sectional schematic view similar to FIG. 32 but withthe system in operation and having an annular cell concentrate region inthe separation chamber.

FIG. 35 is an external front top perspective view of a furtheralternative single use centrifuge structure.

FIG. 36 is a cross-sectional view of the single use structure shown inFIG. 35.

FIG. 37 is an exploded view of the upper disc shape portion of thesingle use structure shown in FIG. 35.

FIG. 38 is a perspective view of the lower piece of the upper disc shapeportion of the structure shown in FIG. 35.

DETAILED DESCRIPTION

In the field of cell culture as applied to bio-pharmaceutical processesthere exists a need to separate cells from fluid media such as fluid inwhich cells are grown. The desired product from the cell culture may bea molecular species that the cell excretes into the media, a molecularspecies that remains within the cell, or it may be the cell itself. Atproduction scale, the initial stages of cell culture process typicallytake place in bioreactors, which may be operated in either batch orcontinuous mode. Variations such as repeated batch processes may bepracticed as well. The desired product often must eventually beseparated from other process components prior to final purification andproduct formulation. Cell harvest is a general term applied to thesecell separations from other process components. Clarification is a termdenoting cell separations in which a cell-free supernatant (or centrate)is the objective. Cell recovery is a term often applied to separationswherein a cell concentrate is the objective. The exemplary arrangementsherein are directed to cell harvest separations in large-scale cellculture systems.

Methods for cell harvest separations include batch, intermittent,continuous and semi-continuous centrifugation, tangential flowfiltration (TFF) and depth filtration. Historically, centrifuges forcell harvest of large volumes of cell culture at production scale arecomplex multiple use systems that require clean-in-place (CIP) andsteam-in-place (SIP) technology to provide an aseptic environment toprevent contamination by microorganisms. At lab scale and for continuouscell harvest processes, smaller systems may be used. The UniFuge®centrifuge system, manufactured by Pneumatic Scale Corporation,described in published application US 2010/0167388, the entiredisclosure of which is incorporated herein by reference, successfullyprocesses culture batches for cell harvest in the range of 3-30liters/minute in quantities of up to about 2000 liters usingintermittent processing. Also incorporated herein in their entirety areU.S. Pat. Nos. 10,384,216 and 9,222,067, which are also owned byPneumatic Scale Corporation, the assignee of the present application.Intermittent processing generally requires periodically stopping bothrotation of the centrifuge bowl and the feed flow in order to dischargeconcentrate. This approach usually works well with lower concentration,high viability cultures, in which large batches can be processed, andthe cell concentrate discharged relatively quickly and completely.

There is sometimes a requirement to harvest cells from highlyconcentrated and/or low viability cell cultures, which contain a highconcentration of cells and cell debris in the material feed, which aresometimes referred to as “high turbidity feeds.” Such high turbidityfeeds can slow down the processing rate in some centrifugal separationsystems, because:

-   -   1. a slower feed flow rate is required to provide increased        residence time in the centrifuge in order to separate small cell        debris particles, and    -   2. the higher concentrations of both cells and cell debris may        result in the bowl filling rapidly with cell concentrate, which        requires the bowl to be stopped to discharge concentrate.

These combined factors may result in a reduced net throughput rate, andunacceptably long cell harvest processing times. In addition to theincreased costs which may be associated with a longer processing time,increased time in the centrifuge may also result in a higher degree ofproduct contamination and loss in the harvesting low viability cellcultures.

A high concentration of cell and cell debris in a material feed may alsoresult in a cell concentrate with a very high viscosity. This may makeit more difficult to completely discharge the cell concentrate from thecentrifuge, even with a prolonged discharge cycle. In some cases, anadditional buffer rinse cycle may be added to obtain a sufficientlycomplete discharge of concentrate. The need to make either or both ofthese adjustments to the discharge cycle further increases theprocessing time, which can make the challenges of processing a largevolume of cell culture more complex and costly.

Scaling up the size of systems, by increasing the bowl size to increasethe length of the feeding portion of the intermittent processing cycleis sometimes not practical because it also results in a proportionatelylonger discharge cycle for the cell concentrate. Another limitation thatmay preclude simple geometric scale-up is variation in scaling of thepertinent fluid dynamic factors. The maximum processing rate of anycentrifuge depends on the settling velocity of the particles beingseparated. The settling velocity is given by a modification of Stokes'law defined by Equation 1:

$\begin{matrix}{v = \frac{\Delta \; {p \cdot r \cdot d^{2} \cdot \omega^{2}}}{18 \cdot \mu}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

where v=settling velocity, Ap is solid-liquid density difference, d isparticle diameter, r is radial position of the particle, ω is angularvelocity, and μ is liquid viscosity. With respect to scale-up geometry,changing the radius of the bowl changes the maximum radial position rthat particles can occupy. Therefore, if the other parameters inEquation 1 are held constant, an increase in bowl radius leads to anincrease in average settling velocity and a gain in throughput for agiven separation efficiency. However, as the radius increases it becomesmore difficult to maintain the angular velocity of the bowl because ofthe increased material strength that may be required, and otherengineering limitations. If a decrease in angular velocity is largerthan the square root of the proportional increase in radius, then theaverage settling velocity and the gain in throughput (which isproportional to radius) both decline.

One of the engineering limitations that must be considered is that theangular velocity needed to rotate the larger bowl may not be practicalto achieve because of the more massive and costly centrifuge driveplatform that would be needed.

In addition if the angular velocity is held constant as the radiusincreases, the forces urging the cells toward the walls of thecentrifuge also increase. When the bowl is rotated at sufficiently highangular velocity to create the desired processing efficiency, the wallsof the container and the cells which accumulate there, experience addedstress. As to the cells, this can cause cell damage by packing the cellsto excessively high concentrations. Cell damage is a drawback inapplications wherein cell viability needs to be maintained and can leadto contamination of products that are present in solution in thecentrate. The higher viscosity resulting from excessively high cellconcentrations is also sometimes a drawback for complete discharge ofthe cell concentrate.

Exemplary arrangements include apparatus and methods for continuous orsemi-continuous centrifugal separation of low viability cell suspensioncultures containing a high concentration of cells and cell debris, at arate suitable for processing large volumes of cell suspensions on acommercial scale. Some exemplary centrifuges are of pre-sterilized,single-use designs and are capable of processing such cell suspensionsat flow rates exceeding 20 liters per minute. This flow capacity enablestotal run times in the range of 2 to 3 hours for a 2000 literbioreactor. Exemplary arrangements of the single-use centrifuge systemsmay be capable of processing about 300 to 2,000 liters of fluid whileoperating at a rate of about 2 to 40 liters per minute.

FIG. 1 discloses a single use centrifuge structure 1000. The centrifugestructure 1000 includes a core structure 1500 (best shown in FIG. 3)comprising a core 1510, upper flanges 1300, lower flanges 1200, and aflexible liner 1100 sealed to both an upper flange 1300 and a lowerflange 1200. The centrifuge structure 1000 also includes a centripetalpump 1400, comprising a pair of stationary paring discs 1410 in arotating pump chamber 1420, and a rotating mechanical seal 1700.

Centrifuge structure 1000 also includes a feed/discharge assembly 2000.The assembly 2000 comprises a plurality of concentric tubes about therotational axis 1525 (labeled in FIG. 12) of the centrifuge 1000. Theinnermost portion of feed/discharge assembly 2000 includes a feed tube2100. A plurality of additional tubes concentrically surround the feedtube 2100, and may include tubes or fluid pathways to permit centratedischarge 2200, concentrate discharge 2500 (see, for example, FIG. 12),or diluent feed 5000 (see, for example, FIG. 12). Each portion of thefeed/discharge connection may be in fluid connection with a portion ofthe interior of the centrifuge 1000, and a collection or feed chamber(not shown) via appropriate fluid connections, and may include furthertubes which are in fluid connection with the concentric tubes to removeor add the centrate, concentrate, or diluents from or to the system.

The upper and lower flanges 1300, 1200, as illustrated in FIG. 1,comprise conical bowls, axially aligned with and concave toward the core1510. Core 1510 comprises a generally cylindrical body with a hollowcylindrical center large enough to accept feed tube 2100 having an axis1525 (labeled in FIG. 12). The upper flange 1300, the core 1510 and thelower flange 1200 may be a unitary structure to provide a strongersupport structure for flexible liner 1100 which is alternativelyreferred to herein as a membrane. In other arrangements, the corestructure 1500 may be formed from a plurality of component parts. Infurther arrangements, the core 1510 and upper flange 1300 may comprise asingle component, with a lower flange 1200 comprising a separatecomponent, or the core 1510 and lower flange 1200 may comprise a singlecomponent with the upper flange 1300 comprising a separate component.

An arrangement of an exemplary unitary core 1510 and upper flange 1300is illustrated in FIG. 3. This unitary component would be joined tolower flange 1200 to create the internal supporting structure 1500 ofthe single use components of centrifuge 1000. This structure anchors theflexible liner 1100 around a fixed internal rigid or semi-rigid supportstructure 1500 at both the top and bottom. When the centrifuge system isin use, the flexible liner 1100 is also supported externally by thewalls of the bowl and cover of the multiple use structure 3000.

The exemplary separation chamber 1550 is an open chamber which isroughly cylindrical in shape, bounded roughly by the exterior surface1515 of the core 1510 and the flexible liner 1100, and by the uppersurface 1210 of the lower flanges 1200 and the lower surface 1310 of theupper flanges 1300. The separation chamber 1550 is in fluid connectionwith the feed tube 2100 via holes 1530 extending from the central cavity1520 of the core 1510 to the exterior surface 1515 of the core 1510. Theseparation chamber 1550 is also in fluid connection with the pumpchamber 1420 via similar holes 1540 through the core structure 1500. Inthis example, holes 1540 angle upward, toward the pump chamber 1420,opening into the separation chamber 1550 just below the junction betweenthe core 1510 and upper flanges 1300. As shown in FIG. 12, holes 1420 or4420 may enter pump chambers at an angle other than upward, includinghorizontally or at a downward angle. In addition, in some arrangementsholes 1420, 4420 may be replaced by slits, or gaps between acceleratorfins.

FIG. 1 also shows a feed/discharge assembly 2000 which includes a feedtube carrier 2300, through which feed tube 2100 extends into theposition shown in FIG. 3, close to the bottom of centrifuge structure1000. In this position the feed tube 2100 can perform both feed anddischarge functions without being moved. Shearing forces during thefeeding process may be minimized by careful design of the gap betweenthe nozzle 2110 of the feed tube 2100 and the upper surface 1210 of thelower flanges 1200, the diameter of the nozzle 2110 of the feed tube2100, and the angular velocity of the centrifuge. U.S. Patent No.6,616,590, the disclosure of which is incorporated herein by referencein its entirety, describes how to select appropriate relationships tominimize the shearing forces. Other suitable feed tube designs whichminimize the shearing forces associated with feeding a liquid cellculture into a rotating centrifuge which are known to those skilled inthe art may also be used.

FIG. 1 further includes a centripetal pump 1400 for discharging centratethrough a centrate discharge path 2200. In the arrangement shown in FIG.1, the centrate pump 1400 is located above the upper flange 1300 in apump chamber 1420. Pump chamber 1420 is a chamber defined by the uppersurface 1505 of the core 1510 and the inner surfaces 1605, 1620 of acentrifuge cover 1600. The centrifuge cover 1600 may include cylindricalwalls 1640 and a mating cap portion 1610 shaped like a generallycircular disc (shown in FIG. 5). The centrifuge cover 1600 may be formedas a unitary body, or from separate components.

As discussed in more detail below, in other arrangements, the shape andposition of the centrate pump chamber 1420 may vary. Chamber 1420 willgenerally be an axially symmetric chamber near the upper end of the corestructure 1500 which is in fluid connection with the separation chamber1550 via holes or slits 1530 which extend from adjacent the exterior ofthe core 1515 into the centrate pump chamber 1420. In some arrangements,as shown most clearly in FIGS. 11 and 12, centrate pump chamber 1420 maybe located in a recess within chamber 1550.

Exemplary centrate pump 1400 comprises a pair of paring discs 1410.Paring discs 1410 are two thin circular discs (plates), which areaxially aligned with the axis 1525 of core structure 1500. In thearrangement illustrated in FIGS. 1-5, paring discs 1410 are heldstationary relative to the centrifuge structure 1000, and are separatedfrom each other by a fixed gap 1415 (labeled 1415 in FIG. 10). The gap1415 between the paring discs 1410 forms part of a fluid connection forremoving centrate from the centrifuge 1000, which permits centrate toflow between the paring discs 1410 into a hollow cylindrical centratedischarge path 2200 surrounding the feed tube carrier 2300, terminatingin centrate outlet 2400.

The exemplary single use centrifuge structure 1000 is contained within amultiple use centrifuge structure 3000. The structure 3000 comprises abowl 3100 and a cover 3200. The walls of the centrifuge bowl 3100support the flexible liner 1100 of centrifuge structure 1000 duringrotation of the centrifuge 1000. In order to do so, the externalstructure of the single use structure 1000 and the internal structure ofthe multiple use structure conform to each other. Similarly, the uppersurface of upper flanges 1200, the exterior of an upper portion of core1510, and a lower portion of the walls 1640 of the centrifuge cover 1600conform to the inner surface of the multiple use bowl cover 3200, whichis also adapted to provide support during rotation. Features of themultiple use bowl 3100 and bowl cover 3200, discussed in more detailbelow, are designed to ensure that shear forces do not tear the liner1100 free from the single use centrifuge structure 1000. In someinstances, an existing multiple use structure 3000 may be retrofittedfor single use processing by selecting a conforming single use structure1000. In other instances, the multiple use structure 3000 may bespecially designed for use with single use structure inserts 1000.

FIG. 2 shows a portion of an exemplary structure for upper flanges 1300,plastic liner 1100, and the cover 3200 of a multiple use centrifugestructure 3000 to illustrate sealing the flexible liner 1100 to theupper flanges 1300. The flexible liner 1100 may be a thermoplasticelastomer such as a polyurethane (TPU) or other stretchable, tough,non-tearing, bio-compatible polymer, while the upper and lower flanges1300, 1200 may be fabricated from a rigid polymer such aspolyetherimide, polycarbonate, or polysulfone. The flexible liner 1100is a thin sleeve, or envelope, which extends between and is sealed tothe upper and lower flanges 1300, 1200, and forms the outer wall ofseparation chamber 1550. The composition of the liner 1100 and of theupper and lower flanges 1300, 1200, and core 1510 described herein areexemplary only. Those skilled in the art may substitute suitablematerials with properties similar to those suggested which are, or maybecome, known.

A thermal bonding attachment process may be used to bond the dissimilarmaterials in the area shown in FIG. 2. The thermal bond 1110 is formedby preheating the flange material, placing the elastomeric polymer atopthe heated flange, and applying heat and pressure to the elastomericfilm liner 1100 at a temperature above the film's softening point. Theplastic liner 1100 is bonded to lower flange 1200 in the same manner.Although a thermal bond 1110 is described herein, it is merelyexemplary. Other means of creating a similarly strong relativelypermanent bond between the flexible film and the flange material may besubstituted, such as by temperature, chemical, adhesive, or otherbonding means.

The exemplary single-use components are pre-sterilized. During theremoval of these components from their protective packaging andinstallation into a centrifuge, the thermal bonds 1110 maintainsterility within the single-use chamber. The stretchable flexible liner1100 conforms to the walls of reusable bowl 3100 when in use. Reusablebowl 3100 provides sufficient support, and the flexible liner 1100 issufficiently elastic, to permit the single use structure 1000 towithstand the increased rotational forces which are generated when thelarger radius centrifuge 1000 is filled with a liquid cell culture orother cell suspension and is rotated with a sufficient angular velocityto reach a settling velocity that permits processing at a rate of about2-40 liters a minute.

In addition to the thermal bond 1110, sealing ridges or “nubbins” 3210may be present on bowl cover 3200 to compress the thermoplasticelastomeric film against the rigid upper flanges 1300, forming anadditional seal. The same compression seals may also be used at thebottom of the bowl 3100 to seal the thermoplastic elastomeric filmagainst the rigid lower flanges 1200. These compression seals supportthe thermal bonded areas 1110, by isolating them from shearing forcescreated by the hydrostatic pressure that develops during centrifugationwhen the chamber is filled with liquid. The combination of the thermalbond 1110 and the compression nubbin 3210 seals has been tested at3000×g, which corresponds to a hydrostatic pressure of 97 psi at thebowl wall. The lining should be sufficiently thick and compressible topermit the nubbins 3210 to compress and grip the flexible liner 1100 yetminimize the risk of tearing near the thermal bond 1110 or compressionnubbins 3210. In one example arrangement, a flexible TPU liner 0.010inch thick sealed without tearing or leaking.

An arrangement corresponding to the illustrations of FIGS. 1-2 has beentested within a bowl that was 5.5 inches in diameter. At 2000×g it had ahydraulic capacity >7 liters/min and successfully separated mammaliancells to 99% efficiency at a rate of 3 liter/min.

In most instances, the upper and lower flanges 1300, 1200 may have ashape similar to that illustrated FIG. 1, but in some instances theupper surface of the single use centrifuge structure may have adifferent shape, as is illustrated in FIGS. 10 and 11. In thearrangements illustrated in FIGS. 10 and 11, rather than having agenerally conical bowl cover 3200, to conform to generally conical upperflanges 1300, both the upper flanges and the bowl cover are relativelydisc-shaped. Those skilled in the art will be able to adapt the sealingtechniques described herein for use with differently shaped sealingsurfaces.

FIGS. 4-5 illustrate an example arrangement with features to improve theefficiency of the centripetal pump 1400. As shown in detail in FIG. 5,this arrangement of an internal structure for single use componentssimilar to that illustrated in FIGS. 1 and 2 includes a plurality ofradial fins 1630 on the inner face 1620 of a cap portion 1610 of thepump chamber 1420. FIG. 5 shows the inner face 1620 of the cap portion1610 of centrifuge cover 1600. The radial fins 1630, may be thin,generally rectangular, radial plates, extending perpendicularly from theinner surface 1620 of the cap portion 1610. In the exemplaryarrangement, six (6) fins 1630 are illustrated, but other arrangementsmay include fewer or more fins 1630. In this arrangement, fins 1630 formpart of the inner face of cap 1620, but in other arrangements maycomprise the upper surface 1620 of pump chamber 1420, which may take aform other than cap 1610. When the centrifuge system 1000 is in use,fins 1630 are located above the paring discs 1410 of the centripetalpump 1400 in the chamber 1420. These fins 1630 transmit the angularrotation of the centrifuge 1000 to the centrate within in the pumpchamber 1420.

This increases the efficiency of the centripetal pump 1400, stabilizingthe gas to liquid interface in the pump chamber 1420 above the paringdiscs 1410, and increasing the size of the gas barrier. The gas barrieris a generally cylindrical column of gas extending from the exterior ofthe feed/discharge mechanism 2000 outward into the pump chamber 1420 tothe inner surface of the rotating centrate. This increase in the size ofthe barrier occurs because the resulting increase in angular velocity ofthe centrate forces the centrate toward the wall of the centrifuge. Whenrotating centrate within the pump chamber 1420 comes into contact withthe stationary paring discs 1410 the resulting friction may decrease theefficiency of the pump 1400. The addition of a plurality of radial fins1630, which rotate with the same angular velocity as the centrate,overcomes any reduction in velocity that might otherwise result from theencounter between the rotating centrate and the stationary paring discs1410.

FIG. 6 shows an exemplary arrangement of a core structure 1500 for usein high turbidity feeds. Core structure 1500 includes a core 1510, upperflange 1300, and lower flange 1200. Core 1510 has a cylindrical centralcavity 1520 adapted to permit feed tube 2100 to be inserted into thecentral cavity 1520. The distance from the central axis 1525 to theexterior of core 1515 (the core width, represented by dashed line 6000in FIG. 6) is larger than the corresponding distance in the arrangementillustrated in FIG. 3. The larger diameter core 1510 decreases the depth(represented by dashed line 6010) of the separation chamber 1550, makingcentrifuge 1000 operate as a shallow pool centrifuge. The depth 6010 ofa separation chamber 1550 is generally the distance between the exteriorof the core 1510 and the flexible liner 1100, labeled in FIGS. 1 and 12.A shallow pool centrifuge is one which has a depth 6010 which is small,relative to the diameter of the centrifuge. As can be seen in theexemplary arrangement illustrated in FIG. 12, in order to facilitateremoval of the cell concentrate, the shallow pool depth 6010 may varyfrom shallower at the bottom of separation chamber 1550 to somewhatdeeper the top of the separation chamber 1550. In some arrangementsillustrated herein, the ratio of the average separation pool depth 6010to the core width is 1:1 or lower. An example of a shallow poolcentrifuge is offered as an optional model of the ViaFuge® centrifugesystem, manufactured by Pneumatic Scale Corporation. The advantage of ashallow pool centrifuge is that it enables separation at higher feedflow rates. This is accomplished by virtue of a higher average g-forcefor a given inner bowl diameter, which creates a higher sedimentationvelocity at a given angular velocity. The resulting enhanced separationperformance is beneficial when separating highly turbid feeds containinga high concentration of cell debris.

The example arrangement of the core structure 1500 which is illustratedin FIG. 6 also includes accelerator vanes 1560 as part of the lowerflange 1200. Accelerator vanes 1560 (as shown in FIG. 12), rather thanholes 1530 through a solid core 1510 (as shown in FIG. 10-11), comprisean alternate arrangement of a fluid connection between the centralcavity 1520 of the core 1510 and the separation chamber 1550.

In the exemplary arrangement of a core structure 1500 shown in FIG. 6,accelerator vanes 1560 comprise a plurality of radially, generallyrectangular, spaced thin plates 1580 extending upward from the upperconical surface of the lower flange 1200. Plates 1580 extend upwardorthogonal to the base of the core 1510. Plates 1580 generally extendradially outward from near the axis 1525 of the core 1510. In theexemplary arrangement, there are 12 plates 1580, as shown most clearlyin FIG. 7. In other arrangements there may be fewer or more than 12plates 1580. In addition, in other arrangements the plates 1580 may becurved in the direction of rotation of the centrifuge 1000, as shown inan exemplary embodiment in FIG. 9. The interior surface of lower flange1200 may be modified to form an elliptical accelerator bowl 1590, withthe curved plates extending upward therefrom. These arrangements areintended to be exemplary, and those skilled in the art may combine themin different ways or may modify these arrangements to further benefitfrom the turbidity reduction these plates and the shape of the lowerflange 1200 and/or an embedded accelerator bowl create.

Further features of an example arrangement of a single use centrifuge1000 which is designed to operate continuously or semi-continuously areillustrated in FIGS. 10-12. The exemplary arrangement illustrated inFIG. 10 includes a second centripetal pump 4400 for removal of cellconcentrate. Centripetal pump 4400 for the removal of cell concentrateis located above the centripetal pump 1400 for removal of centrate.Centripetal pump 4400 includes a pump chamber 4420 and paring discs4410. A plurality of holes or continuous slits 4540 extend from theupper outer circumference of the separation chamber 1550 into pumpchamber 4420, providing fluid connection from outer portion of theseparation chamber 1550 to the second pump chamber 4420. As with pumpchamber 1400, pump chamber 4400 may have a different shape than thatillustrated in FIGS. 10-12, but will generally be an axially symmetricchamber near the upper end of the core structure 1500 which is in fluidconnection with the separation chamber 1550. As with pump chamber 1400,the pump chamber may be partially or entirely recessed within corestructure 1500. If a centrate pump chamber 1400 is present near theupper end of the core structure 1500, the cell concentrate pump chamber4400 will generally be located above it. A pump chamber 4400, for theremoval of cell concentrate, will be in fluid connection with separationchamber 1550 via holes or slits 4540 which extend from adjacent theouter upper wall of separation chamber 1550, in order to collect theheavier cell concentrate which is urged there by centrifugal forces.

In the arrangement illustrated in FIG. 10, the paring discs 4410 used inthe concentrate discharge pump 4400 are approximately the same radius asthose used in the centrate discharge pump 1400, and are rotationallyfixed. In other arrangements, such as the one shown in FIG. 11, theparing discs 4410 in the concentrate discharge pump 4400 may have alarger radius than those in the centrate discharge pump 1400, with acorrespondingly larger pump chamber 4420. Paring discs of variousintermediate diameters may be used as well. The optimum diameter willdepend on the properties of the cell concentrate that is to bedischarged. Larger diameter paring discs have a higher pumping capacity,but create greater shear.

In the arrangements illustrated in FIGS. 1, 4, and 10, the paring discs4410 in the concentrate discharge pump 4400 are rotationally fixed. Inother arrangements, such as the one shown in FIG. 11, paring discs in4410 may be adapted to rotate with an angular velocity between zero andthe angular velocity of the centrifuge 1000. The desired angularvelocity can be controlled by a number of mechanisms that are known tothose skilled in the art. An example of a means of control is anexternal slip clutch that allows the paring discs 4410 to rotate at anangular velocity that is a fraction of that of the centrifuge 1000.Other means of controlling the angular velocity of the paring discs willbe apparent to those skilled in the art.

In the arrangements illustrated in FIGS. 1, 4, 10-12, the gaps 1415,4415 between paring discs 1410 and 4410 are fixed. In otherarrangements, such as shown in FIG. 13, the gaps 1415, 4415 betweenparing discs 1410 and 4410 may be adjustable, in order to control theflow rate at which centrate or concentrate are removed from thecentrifuge 1000. One of each pair of paring discs 1410 and 4410 isattached to a vertically moveable throttle tube 6100. Throttle tube 6100may be moved up or down in order to narrow or widen the gap 1415, 4415between each pair of the paring discs 1410, 4410. In addition, anexternal peristaltic pump 2510 (not shown) may be added to theconcentrate removal line 2500 (not shown) to aid in removal ofconcentrate. This pump 2510 may be controlled by a sensor 4430 in thepump chamber 4420. The sensor 4430 (not shown) may also be used tocontrol a diluent pump 5150 in order to synchronize concentrate removalwith the addition of diluents.

Also illustrated in FIG. 13 is an arrangement in which the centrate pump1400 is located at the base of the centrifuge 1000. In the arrangementillustrated in FIG. 13, a centrate well 1555 is created between the pumpchamber 1420 and the flexible liner 1100. Holes 1530 extend from thecore 1510, below the pump chamber 1420, into the centrate well 1555. Inaddition, in the exemplary arrangement illustrated, holes 1540 extendfrom the separation chamber 1550, adjacent the exterior surface 1515 ofthe core 1510, into the pump chamber 1420 to permit the centrate to beremoved using centrate pump 1400. Holes 4540 may also extend between theseparation chamber 1550, adjacent its outer upper surface, into pumpchamber 4420 to permit cell concentrate to flow into pump chamber 4420to be removed using centripetal pump 4400.

As noted above, in the exemplary arrangement illustrated, the gaps 1415,4415 between the paring discs 4410 and 1410 may be adjustable by use ofa throttle tube 6100 connected to one of each pair of paring discs 4410,1410. Throttle tube 6100, and the attached one of each paring disc pair4410, 1410, may be moved up or down to narrow or widen gaps 1415, 4415.In the exemplary arrangement illustrated, the throttle tube 6100 isattached to the lower and upper paring disc of paring disc pairs 4410,1410, respectively. In other arrangements the attachment may bereversed, may be used to throttle a single centripetal pump, or may beused to throttle both in parallel (rather than opposition as illustratedin FIG. 13).

As can be seen in the arrangements illustrated in FIGS. 10-12, the wallof the solid multiple use bowl 3100 is thicker at the base than it is inthe upper portion, in order to create an internal truncated cone shapeto support single use centrifuge structure 1000 which has a smallerradius at the lower end than at the upper end. This larger radius at theupper end of the separation chamber 1550 moves the denser cellconcentrate toward the upper outer portion of the separation chamber1550 and into centripetal pump chamber 4420. In the arrangementillustrated, the truncated cone shape is created by a multiple use bowl3100 with a wall which is thicker at the base than it is in the upperportion. Those skilled in the art will recognize that a multiple usebowl 3100 having an internal truncated cone shape may also include wallsof uniform thickness, and that there may be other variations whichcreate the desired internal shape for the multiple use bowl 3100.

In the example arrangements illustrated in FIGS. 10-12, feed mechanism2000 also includes an additional pathway for the removal of cells, orcell concentrate. In the arrangement illustrated in FIG. 1, thecylindrical pathway 2200 around the feed tube 2100 is used to removecentrate. The arrangements illustrated in FIGS. 10-12 also include, aconcentric cylindrical pathway for the removal of cells or cellconcentrate, referred to as a cell discharge tube 2500. Cell dischargetube 2500 surrounds the centrate removal pathway 2200. If the centrifugeis designed to be used with a concentrate that is expected to be veryviscous, an additional concentric cylindrical fluid pathway 5000 may beadded around the feed tube 2100 to permit the diluents to be introducedinto the cell concentrate pump chamber 4420 in order to decrease theviscosity of the concentrate. The diluent pathway 5000, in the exemplaryarrangements illustrated in FIG. 12, comprises a concentric tubesurrounding the cell discharge pathway, and opens at the lower end intoa thin disc-shaped fluid pathway 5100 above paring discs 4410,discharging near the outer edge of the paring discs 4410 to providefluid communication with the pump chamber 4420. Injecting the diluent bythis means, and in this location, limits the diluent to mixing with, andbeing discharged with, the concentrate rather than being introduced intothe centrate, which may be undesirable in some applications. Inalternative arrangements, the diluents may be introduced directly ontothe upper surface of the paring discs and allowed to spread radiallyoutward, or onto a separate disc located above the paring discs.

The choice of diluent will depend on the objectives of the separationprocess and the nature of the cell concentrate that is to be diluted. Insome cases a simple isotonic buffer or deionized water can serve as thediluent. In other cases, diluents that are specific to the properties ofa cell concentrate may be advantageous. For example, in production scalebatch cell culture operated at low cell viability, flocculants arecommonly added to the culture as it is being fed to a centrifuge tocause cells and cell debris to flocculate or agglomerate into largerparticles, which facilitates their separation by increasing their rateof sedimentation. Since both cells and cell debris carry negativesurface charges, the compounds used as flocculants are typicallycationic polymers, which carry multiple positive charges, such aspolyethyleneimine. By virtue of their multiple positive charges, suchflocculants can link negatively charged cells and cells debris intolarge agglomerates. An undesirable consequence of the use of suchflocculants is that they further increase the viscosity of cellconcentrates. Therefore, a particularly useful diluent in thisapplication is a deflocculant that will disrupt the bonds that increasethe viscosity of the cell concentrate. Examples of deflocculants includehigh salt buffers such as sodium chloride solutions ranging inconcentration from 0.1 M to 1.0 M. Other deflocculants that may beuseful in reducing the viscosity of cell concentrate are anionicpolymers such as polymers of acrylic acid.

In the case of a cell concentrate wherein cell viability is to bemaintained, a diluent can be chosen that is a shear protectant, such asdextran or Pluronic F-68. The use of a shear protectant, in combinationwith an isotonic buffer, will enhance the survival and viability ofcells as they are being discharged from the centrifuge.

The exemplary centrifuge illustrated in FIG. 4 operates as describedbelow. During a feed cycle, a feed suspension flows into the rotatingbowl assembly through feed tube 2100. As the feed suspension enters thecentral cavity 1520 of core 1510 near lower flange 1200, it is urgedoutward along the upper surface of lower flange 1200 by centrifugalforces, passing into the separation chamber 1550 through holes 1530 incore 1510.

Centrate collects in the separation chamber 1550, a hollow, roughlycylindrical space below the upper flange 1300 surrounding core 1510. Thecentrate flows upward from its entrance into the separation chamberthrough holes 1530 until it encounters holes 1540 between the separationchamber 1550 and the pump chamber 1420 in the upper portion of theseparation chamber 1550, adjacent the core 1410. Particles of densityhigher than that of the liquid are moved toward the outer wall of theseparation chamber 1550 by sedimentation (particle concentrate), awayfrom holes 1530. When the rotation of the centrifuge 1000 is stopped,the particle concentrate moves downward under the influence of gravityto the nozzle 2110 of the feed tube 2100 for removal via the combinedfeed/discharge mechanism 2000.

During rotation, the centrate enters the centrate pump chamber 1420through holes 1540. Within the pump chamber 1420, the rotating centrateencounters stationary paring discs 1410, which convert the kineticenergy of the rotating liquid into pressure which urges the centratebeing discharged upward through the centrate discharge path 2200 withinthe feed/discharge mechanism 2000 and out through the centrate dischargetube 2400.

The efficiency of the centripetal pump 1400 is increased by addingradial fins 1630 on the inner surface 1620 of the cap portion 1610 ofthe rotating pump 1400. These fins 1630 impart the angular momentum ofthe rotating assembly to the centrate in the pump chamber 1420, whichmight otherwise slow because of friction when the rotating centrateencounters the stationary paring discs 1410. The centripetal pump 1400provides an improved means of centrate discharge, over mechanical seals,because of the gas liquid interface within the pump chamber 1420. Thegas within the pump chamber 1420 is isolated from contamination by theexternal environment by the rotating seal 1700. Because the centratebeing discharged between the paring discs 1410 does not come intocontact with air, either during the feed or discharge process, it avoidsthe excessive foaming that often occurs when the discharge processintroduces air into the cell culture.

In the centrifuge 1000 arrangement illustrated in FIGS. 4-5, cellconcentrate is discharged by periodically stopping bowl rotation and thefeed flow and then pumping out the cell concentrate that has beencollected along the outer walls of the separation chamber 1550. Thisprocess is known as intermittent processing. When the volumetriccapacity of the separation chamber 1550 is reached, centrifuge rotationis stopped. The cell concentrate moves downward toward nozzle 2110 offeed tube 2100, where the concentrate is withdrawn by pumping it outthrough the feed tube 2100. Appropriate valving (not shown) external tothe centrifuge 1000 is used to direct the concentrate into a collectionvessel (not shown). If the entire bioreactor batch has not yet beencompletely processed, then bowl rotation and feed flow are resumed, andis followed by additional feed and discharge cycles until the full batchhas been processed.

As noted above, when the cell culture is concentrated or containssignificant cell debris, the process described above slows down becauseresidence time must be increased to capture small debris particles,which necessitates a slower feed flow rate and the separation chamber1550 fills rapidly and rotation must be halted frequently and repeatedlyfor each culture batch. In addition, the cell concentrate tends to bemore viscous so gravity does not work as efficiently to drain the cellconcentrate to the bottom of the centrifuge 1000 so it takes longer and,in some instances, may require a wash to remove the remaining cells.

The single use centrifuge, as modified in the exemplary arrangementsillustrated in FIGS. 6-13, creates a higher average settling velocitywithout an increase in angular velocity, permits the centrifuge 1000 torun continuously or semi-continuously, and allows a diluent to be addedto the cell concentrate during the cell removal process so that theremoval of cells is more easily and more completely accomplished.

A single use centrifuge structure 1000 shown in FIGS. 6-12 operate asdiscussed herein. Feed suspension enters the single use centrifugestructure 1000 via feed tube 2100. As the feed suspension encountersaccelerator vanes 1560, the vanes 1560 impart an angular velocity to thefeed suspension which approaches the angular velocity of the single usecentrifuge 1000. The use of vanes 1560, rather than holes 1530, providesfor a greater volume of feed suspension to enter the separation chamber1550 at a slower radial velocity, avoiding the jetting which occurs whenthe feed suspension is forced through holes 1530 having smallercross-sectional openings than the openings between the vanes 1560. Thisreduction in velocity of the feed stream as it enters the separationzone, or pool, minimizes disruption of the liquid contents of the pool,which allows for more efficient sedimentation.

As the centrifuge 1000 rotates, the particles which are denser than thecentrate are urged toward the outside of the separation chamber 1550,leaving the particle free centrate near the core 1510. The centrifugebowl 3100 has the shape of an inverted truncated cone, with a widerradius at the upper end than the lower end. The centrifugal force causesthe particles to collect in the upper and outer portion of the chamber.The centrifuge 1000 may operate with semi-continuous discharge ofconcentrate. The centrate discharge works, generally, as described withrespect to FIG. 4. The cell concentrate discharge works similarly, withthe cell concentrate collecting near the upper outer portion of theseparation chamber 1550 and entering the concentrate discharge pumpchamber 4400 via holes 4540 adjacent the upper outer wall of theseparation chamber 1550.

The rate of feed of suspension, as well as the angular velocity ofrotation, may be monitored using sensors, including without limitation avibration sensor system such as the one described in U.S. Pat. No.9,427,748, incorporated by reference herein in its entirety. Such asensor system permits the centrifuge to be filled at a lower rate untilthe sensor arrangement indicates the centrifuge is nearly full, then toadjust the feed rate and angular velocity appropriately in response tothis information. Typically, the feed rate will be decreased or stoppedonce the centrifuge is nearly full and the angular velocity will beincreased in order to increase the settling velocity and once thesettling and discharge is essentially complete, the cycle will berepeated. If the system is optimized using the additional featuresdescribed herein to diminish the need to interrupt the process, it maybe possible to operate the system continuously, or nearly continuously,at the angular velocity needed for settling.

With semi-continuous concentrate discharge, the suspension continues tobe fed into the centrifuge 1000, using concentrate pump 4400 operatingintermittently to remove concentrate. The operation of concentrate pump4400 may be controlled by an optical sensor in the concentrate dischargeline that indicates the presence or absence of concentrate beingdischarged. In lieu of a concentrate pump 4400, the discharge cycle maybe managed electronically using a controller and sensors which determinewhen to open and shut a valve for the most efficient processing of thefluid suspension.

The average rate of discharge may further be controlled by using acentrifuge 1000 with an adjustable gap between the paring discs 4410,1410. It should be noted that it may only be desired or necessary forone set of paring discs 4410, 1410 to be adjustable. The gap betweenparing discs 4410, 1410 (which forms a part of the fluid pathway out ofthe centrifuge 1000) may be opened to permit flow, or closed to shut theflow off, acting as an internal valve. Depending on the desired product,or the characteristics of the product, it may also be useful to widen ornarrow the gap 4415, 1415 between paring discs 4410, 1410. Changing thegap affects both pumping and shear rates associated with the pairingdiscs.

The rate of removal of concentrate and centrate from the centrifuge1000, and the viability of the concentrate removed, may be furthercontrolled using a number of features of exemplary arrangements shown inFIGS. 4-13. Accelerator fins 4630, similar to those in the centrate pumpchamber 1420, may be added to concentrate pump chamber 4420. Theaddition of accelerator fins 4630 increases the rate at which theconcentrate may be removed, by overcoming some of the slow down due tofriction between the moving concentrate and the paring discs 4410. Inaddition to accelerator fins 4630 in the upper surface of the pumpchamber 4420, such fins 4630 may also be added to a lower surface in thepump chamber 4420 to increase their effectiveness. A further feature maybe the substitution of slits for holes 1540, 4540, which minimizes theshear on material entering the pump chambers 1420, 4420.

If viability of the concentrate is a concern, rotatable paring discs4410 may be included in pump chamber 4420, which reduce the shearimparted to the concentrate as it contacts the surfaces of the paringdiscs 4410. The rotation rate of paring discs 4410 may be adjusted to arate somewhat between stationary and the rate of rotation of theseparation chamber 1550 to balance concentrate viability against therate of discharge. The desired angular velocity can be controlled by anumber of mechanisms that are known to those skilled in the art. Anexample of a means of control is an external slip clutch that allows theparing discs to rotate at an angular velocity that is a fraction of thatof the centrifuge. The use of slip clutches is well known to thoseskilled in the art. In addition, there may be means other than slipclutches to adjust the angular velocity that will be apparent to thoseskilled in the art.

A peristaltic pump 2510 may be also used to make removal of theconcentrate more efficient and reliable, particularly with veryconcentrated feed suspensions. Using a peristaltic pump 2510 permits theuser to more precisely control the rate of flow of the concentrate fromthe centrifuge 1000 than is possible relying on centripetal pumps 4400,alone, because the rate of centripetal pumps are not as easilyadjustable as the rate of a peristaltic pump 2510.

In addition, a diluent, such as sterile water or a buffer, may be pumpedinto the concentrate pump chamber 4420 through the diluent pathway 5000using a diluent pump 5150 in order to cut the viscosity of theconcentration. A more complete discussion of useful diluents can befound above. The rate at which either or both of the peristaltic pump2510 or the diluent pump 5150 operates may be controlled by an automatedcontroller (such as is later discussed) responsive to a concentrationsensor 4430 located in the concentrate discharge connection 2500. Thecontroller may be programmed to start, stop, or modify the pump rate forboth diluent addition and concentrate removal responsive to the particleconcentration in the concentrate, either independently, responsive to aconcentration sensor 4430, in conjunction with a standard feed/dischargecycle, or as a combination.

FIG. 16 shows an alternative example arrangement of a core used inconnection with a centrifuge that provides continuous separationprocessing to produce continuous concentrate and centrate feeds. Thecore 10 is similar to those previously discussed that is configured tobe positioned in the rotatable bowl of a centrifuge. The centrifuge bowland the core rotate about an axis 12 during processing. The apparatusincludes a stationary assembly 14 and a rotatable assembly 16.

As with the previously described arrangements, the stationary assembly14 includes a feed tube 18. The feed tube 18 is coaxial with the axis 12and terminates in an opening 20 adjacent the bottom of the separationchamber or cavity 22 of the core. The stationary assembly furtherincludes a centrate centripetal pump 24. The exemplary arrangement ofthe centrate centripetal pump 24, which is described in greater detailhereafter, includes inlet opening 26 and an annular outlet opening 28.The annular outlet opening is in fluid connection with a centrate tube30. The centrate tube extends in coaxial surrounding relation with thefeed tube 18.

In this exemplary arrangement, the centrate centripetal pump 24 ispositioned in a centrate pump chamber 32. The centrate pump chamber isdefined by walls which are part of the rotatable assembly, and whichduring operation provide for the inlet openings 26 of the centratecentripetal pump to be exposed to a pool of liquid centrate.

The exemplary arrangement further includes a concentrate centripetalpump 34. The concentrate centripetal pump 34 of the exemplaryarrangement may also be of a construction like that later discussed indetail. In the exemplary arrangement the concentrate centripetal pump 34includes inlet openings 36 positioned in a wall that bounds the annularperiphery of the centripetal pump. It should be noted that theconcentrate centripetal pump 34 has a greater peripheral diameter thanthe peripheral diameter of the centrate pump. The concentrate pumpfurther includes an annular outlet opening 38. The annular outletopening 38 is in fluid connection with a concentrate outlet tube 40. Theconcentrate outlet tube extends in coaxial surrounding relation with thecentrate tube 30.

In the exemplary arrangement the inlet openings 36 of the concentratecentripetal pump are positioned in a concentrate pump chamber 42. Theconcentrate pump chamber is defined by walls of the rotatable assembly16. During operation, the inlet openings 36 of the concentratecentripetal pump are exposed to concentrate in the concentrate pumpchamber 42. The concentrate pump chamber 42 is bounded vertically by atop portion 44. At least one fluid seal 46 extends between the outercircumference of the outlet tube 40 and the top portion 44. Theexemplary seal 46 is configured to reduce the risk of fluid escapingfrom the interior of the separation chamber and to prevent introductionof contaminants from the exterior area of the core therein.

During operation of the centrifuge, the bowl and the core including thecavity or separation chamber is rotated about the axis 12 in arotational direction. Rotation in the rotational direction is operativeto separate cell suspension that is introduced through the feed tube 18,into centrate which is discharged through the centrate tube 30 andconcentrate which is discharged through the concentrate outlet tube 40.

Cell suspension enters the separation chamber 22 through the tubeopening 20 at the bottom of the separation chamber. The cell suspensionis moved outwardly via centrifugal force and a plurality of acceleratorvanes 48. As the suspension is moved outwardly by the accelerator vanes,the cell suspension material is acted upon by the centrifugal force suchthat the cell material is caused to be moved outwardly toward theannular tapered wall 50 that bounds the outer side of the separationchamber. The concentrated cellular material is urged to move outwardlyand upwardly as shown against the tapered wall 50 and through aplurality of concentrate slots 52. The concentrate material movesupwardly beyond the concentrate slots and into the concentrate pumpchamber 42 from which the concentrate is discharged by the concentratecentripetal pump 34.

In the exemplary arrangement, during operation the cell free centrate ispositioned in proximity to a vertical annular wall 54 which bounds theinside of the separation chamber 22. The centrate material movesupwardly through centrate holes 56 in the annular base structure thatbounds the centrate pump chamber 32. The centrate moves upwardly throughthe centrate holes 56 and forms a pool of liquid centrate in thecentrate chamber. From the centrate chamber, the centrate is movedthrough operation of the centrate centripetal pump 24 and delivered fromthe core through the centrate tube 30.

In the exemplary arrangement of FIG. 16, the concentrate and centratepumps may have a configuration generally like that shown in FIG. 17. InFIG. 17, the centrate centripetal pump 24 is represented in an isometricexploded view. As shown in FIG. 17, the exemplary centripetal pump has adisc-shaped body that is comprised of a first plate 58 and a secondplate 60. During operation, the first plate and the second plate areheld in releasible engaged relation via fasteners which are representedby screws 62. Of course it should be understood that in otherarrangements, other configurations and fastening methods may be used.

In the exemplary arrangement, the second plate 60 includes walls thatbound three sides of curved volute passages 64. It should be understoodthat while in the exemplary arrangement, the centripetal pump includes apair of generally opposed volute passages 64. In other arrangements,other numbers and configurations of volute passages may be used.

In the exemplary arrangement, the first and second plates make up thedisc-shaped body of the centripetal pump which has an annular verticallyextending wall 67 which defines an annular periphery 66. Inlet openings68 to the volute passages 64 extend in the annular periphery. An annularcollection chamber 70 extends in the body radially outwardly from theaxis 12 and is fluidly connected to the volute passages. The annularcollection chamber 70 receives the material that enters the inletopenings 68. The annular collection chamber 70 is in fluid connectionwith an annular outlet opening that is coaxial with the axis 12. In theexemplary arrangement for the centrate centripetal pump, the annularoutlet opening is an annular space which extends between the outer wallof feed tube 18 and the inner wall of second plate 60 which outlet isfluidly connected to the centrate outlet tube 30.

In the exemplary arrangement each of the volute passages 64 isconfigured such that the volute passages are curved toward therotational direction of the bowl and separation chamber, the rotationaldirection is represented by Arrow R in FIG. 17. In the exemplaryarrangement, the vertically extending walls 74 which bound the volutepassages and which face the rotational direction, are each curved towardthe rotational direction. The curved configuration of the walls 74 whichbound the volute passages horizontally, provide for the enhanced pumpingproperties of the exemplary arrangement. Further, the opposed boundingwall 76 of each volute passage in the exemplary arrangement has asimilar curved configuration. The curved configuration of the verticallyextending walls that bound the volute passages horizontally provide fora constant cross-sectional area of each volute passage from therespective inlet to the collection chamber. This consistentcross-sectional area is further achieved through the use of a generallyflat wall 78 which extends between walls 74 and 76 and which bounds thevolute passage vertically on one side. Further in the exemplaryarrangement the first plate 58 includes a generally planar circular face80 on its side which faces inwardly when the plates are assembled toform the disc-shaped body of the centripetal pump. In this exemplaryarrangement, the face 80 serves to vertically bound the sides of bothvolute passages 64 of the centripetal pump.

Of course it should be understood that this exemplary arrangement whichincludes a pair of plates, one of which includes a recess with wallswhich bound three of the four sides of the curved volute passages andthe other of which includes a surface that bounds the remaining side ofthe volute passages is exemplary. It should be understood that in otherarrangements, other configurations and structures may be used.

In the exemplary centripetal pump structure shown in FIG. 16, thecentripetal pump structures are utilized and have the capability formoving more liquid than comparably sized paring disc-type centripetalpumps. Further, the exemplary configuration produces less heating of theliquid than comparable paring discs.

Further in the exemplary arrangement as previously discussed, theannular periphery of the centrate centripetal pump 24 has a smallerouter diameter than the periphery of the concentrate centripetal pump34. This configuration is used in the exemplary arrangement to avoid thecentrate centripetal pump removing too much liquid from the pool ofliquid centrate which forms in the centrate pump chamber 32. Assuringthat there is sufficient liquid centrate within the centrate pumpchamber, helps to assure that waves do not form in the centrate adjacentto the inlets of the centrate centripetal pump. The formation of waveswhich could result from less than sufficient liquid centrate, may causevibration and other undesirable properties of the centrifuge and core.

The larger annular periphery of the concentrate pump of the exemplaryarrangement causes material to preferentially flow out of the core viathe concentrate centripetal pump. In exemplary arrangements, the flow ofconcentrate downstream of the concentrate output tube 40 can becontrolled to control the ratio of centrate flow to concentrate flowfrom the core.

Further in exemplary arrangements, utilizing centripetal pumps havingthe configurations described, the properties and flow characteristics ofthe centrifuge may be tailored to the particular materials andrequirements of the separation processing being performed. Specificallythe diameters of the annular periphery of the centripetal pumps may besized so as to achieve optimum properties for the particular processingactivity. For example, the larger the diameter of the periphery of thecentripetal pump, the greater flow and pressure at the outlet that canbe achieved. Further the larger diameter tends to produce greater mixingthan a relatively smaller diameter. However, the larger diameter alsoresults in greater heating than a smaller peripheral diameter of acentripetal pump. Thus to achieve less heating, a smaller diameterperiphery may be used. Further it should be understood that differentsizes, areas and numbers of inlet openings and different volute passageconfigurations may be utilized to vary flow and pressure properties asdesired for purposes of the particular separation process.

FIG. 19 shows schematically an exemplary system which is utilized tohelp assure positive pressure within a separation chamber which isalternatively referred to herein as a cavity, during cell suspensionprocessing. As discussed in connection with previous exemplaryarrangements, it is generally desirable to assure positive pressureabove atmospheric pressure at all times within the separation chamber.Doing so reduces the risk that contaminants are introduced into theseparation chamber by infiltrating past the one or more fluid sealswhich operatively extend between the stationary assembly and therotatable assembly of the core. Further as previously discussed, it isalso generally desirable to maintain air at positive pressure within theseparation chamber in contact with the interior face of the fluid seal.The presence of an air pocket adjacent the seal avoids the seal cominginto contact with the material being processed and further helps toreduce the risk of contaminant introduction into the processed materialas well as the escape of any material from the separation chamber.

The exemplary system described in connection with FIG. 19 serves tomaintain a consistent positive pressure in the separation chamber andreduces the risk of the introduction of contaminants and the escape ofprocessed material.

As schematically shown in FIG. 19, the centrifuge includes a rotatablebowl 82. The centrifuge bowl is rotatable about an axis 84 by a motor 86or other suitable rotating device.

The exemplary centrifuge structure shown includes a rotatable single usecore 88 which bounds a cavity 90 which is alternatively referred toherein as a separation chamber.

Like other previously described arrangements, the exemplary coreincludes a stationary assembly which includes a suspension inlet feedtube 92 which has an inlet opening 94 positioned adjacent to the bottomarea of the cavity. The stationary assembly further includes at leastone centripetal pump 96. The centripetal pump of the exemplaryarrangement includes a disc-shaped body with at least one pump inlet 98adjacent the periphery thereof and a pump outlet 100 adjacent the centerof the centripetal pump. The pump outlet is in fluid connection with acentrate outlet tube 102. The centrate outlet tube extends in coaxialsurrounding relation of the suspension inlet tube in a manner similar tothat previously discussed. The rotatable top portion 104 of the fluidcontaining separation chamber is in operative connection with at leastone seal 106 which operates to fluidly seal the cavity of the core withrespect to the inlet tube and the outlet tube. The at least one seal 106extends operatively in sealing relation between the outer annularsurface of the centrate outlet tube 102 which is stationary, and therotatable top portion 104 of the core which has an upper internal wallwhich internally bounds the cavity 90 as shown.

In the exemplary arrangement the inlet tube 92 is fluidly connected to apump 108. Pump 108 in an exemplary arrangement is a peristaltic pumpwhich is effective to pump cell suspension without causing damagethereto. Of course it should be understood that this type of pump isexemplary and in other arrangements, other types of pumps may be used.Further in the exemplary arrangement the pump 108 is reversible. Thisenables the pump 108 to act as a feed pump so as to be able to pump cellsuspension from an inlet line 110 and into the inlet tube at acontrolled rate. Further in the exemplary arrangement, the pump 108 mayoperate as a concentrate removal or discharge pump after the cellconcentrate has been separated by centrifugal action. In performing thisfunction, the pump 108 operates to pump cell concentrate out of theseparation chamber by reversing the flow of material in the inlet tube92 from that when cell suspension is fed into the separation chamber.The cell concentrate is then pumped to a concentrate line 112. Asrepresented in FIG. 19, the inlet line 110 and concentrate line 112 canbe selectively opened and closed by valves 114 and 116 respectively. Inthe exemplary arrangement, valves 114 and 116 comprise pinch valveswhich open and close off flow through flexible lines or tubing. Ofcourse it should be understood that this approach is exemplary and inother arrangements, other approaches may be used.

In the exemplary system, the centrate outlet tube 102 is fluidlyconnected to a centrate discharge line 118. The centrate discharge lineis fluidly connected to a centrate discharge pump 120. In the exemplaryarrangement, the centrate discharge pump 120 is a variable flow ratepump which can have the flow rate thereof selectively adjusted. Forexample in some exemplary arrangements, the pump 120 may include aperistaltic pump which includes a motor, the speed of which may becontrolled so as to selectively increase or decrease the flow ratethrough the pump. The outlet of the centrate discharge pump delivers theprocessed centrate to a suitable collection chamber or other processingdevice.

In the exemplary arrangement schematically represented in FIG. 19, apressure damping reservoir 122 is fluidly connected to the centratedischarge line 118 fluidly intermediate of the centrate outlet tube 102and the pump 120. In the exemplary arrangement, the pressure dampingreservoir includes a generally vertically extending vessel with aninterior area configured for holding liquid centrate in fluid tightrelation. The pressure damping reservoir includes a bottom port 124which is fluidly connected to the centrate discharge line 118.

On an opposed side of the reservoir 122 is a top port 126. The top portis exposed to air pressure. In the exemplary arrangement, the top portis exposed to air pressure from a source of elevated air pressureschematically indicated 128. In exemplary arrangements, the source ofelevated pressure may include a compressor, an air storage tank or othersuitable device for providing a source of elevated air pressure aboveatmospheric pressure within the range needed for operation of thesystem. Air from the source of elevated pressure 128 is passed through asterile filter 130 to remove impurities therefrom. A regulator 132 isoperative to maintain a generally constant air pressure level aboveatmospheric at the top port of the pressure damping reservoir. Inexemplary arrangements, the air pressure regulator comprises anelectronic fast acting regulator to help assure that the generallyconstant air pressure at the desired level is maintained. The exemplaryfast acting regulator 132 operates to rapidly increase the pressureacting at the top port 126 when the pressure falls below the desiredlevel, and relieves pressure rapidly through the regulator in the eventthat the pressure acting at the top port is above the set value of theregulator.

In some arrangements the regulator outlet may also be in operative fluidconnection with the interior of the top portion 104 of the separationchamber through an air line 143 shown schematically in phantom. In suchexemplary arrangements the outlet pressure of the regulator that acts onthe top port 126 of the reservoir also acts through the air line 143 onthe air pocket inside of the separation chamber which extends downwardto a level in the cavity above the centripetal pump inlet and on theinterior of the at least one seal 106 and radially from a regionproximate to the axis 84 to the upper internal wall on the inside of thetop portion 104. In the exemplary arrangement the line 143 applies thepositive pressure to the area within the separation chamber below the atleast one seal through at least one segregated passage that extendsthrough the stationary structures of the assembly which includes thecentrate outlet tube 102 and the inlet feed tube 92. The at least oneexemplary segregated passage of the air line 143 applies the airpressure to the interior of the top portion 104 through at least one airopening 145 to the separation chamber. The exemplary at least oneopening 145 is positioned outside the exterior surface of the outlettube 102, above the inlet 98 to the centripetal pump and below the atleast one seal 106. Of course it should be understood that thisdescribed structure for the exemplary air line that provides positiveair pressure to the air pocket in the separation chamber and on theinner side of the at least one seal is exemplary, and in otherarrangements, other structures and approaches may be used.

In the exemplary arrangement of the pressure damping reservoir 122, anupper liquid level sensor 134 is configured to sense liquid centratewithin the interior of the pressure damping reservoir. The upper liquidlevel sensor is operative to sense liquid at an upper liquid level. Alower liquid level sensor 136 is positioned to sense liquid in thereservoir at a lower liquid level. A high liquid level sensor 138 ispositioned to detect a high liquid level in the reservoir above theupper liquid level. The high liquid level sensor is positioned so as tosense a liquid level at an unacceptably high level so as to indicate anabnormal condition which may require shutting down the system or takingother appropriate safety actions. In the exemplary arrangement, theliquid level sensors 134, 136 and 138 comprise capacitive proximitysensors which are suitable for sensing the level of the liquid centrateadjacent thereto within the pressure damping reservoir. Of course itshould be understood that these types of sensors are exemplary and inother arrangements, other sensors and approaches may be used.

The exemplary arrangement further includes other components as may beappropriate for the operation of the system. This may include othervalves, lines, pressure connections or other suitable components forpurposes of carrying out the processing and handling of the suspension,centrate and concentrate as appropriate for the particular system. Thismay include additional valves such as valve 140 shown schematically forcontrolling the open and closed condition of the centrate discharge line118. The additional lines, valves, connections or other items includedmay vary depending on the nature of the system.

The exemplary system of FIG. 19 further includes at least one controlcircuit 142 which may be alternatively referred to as a controller. Theexemplary at least one control circuit 142 includes one or moreprocessors 144. The processor is in operative connection with one ormore data stores schematically indicated 146. As used herein, aprocessor refers to any electronic device that is configured to beoperative via processor executable instructions to process data that isstored in the one or more data stores or received from external sources,to resolve information, and to provide outputs which can be used tocontrol other devices or carry out other actions. The one or morecontrol circuits may be implemented as hardware circuits, software,firmware or applications that are operative to enable the controlcircuitry to receive, store or process data and to carry out otheractions. For example the control circuits may include one or more of amicroprocessor, CPU, FPGA, ASIC or other integrated circuit or othertype circuit that is capable of performing functions in the manner of anelectronic computing device. Further it should be understood that datastores may correspond to one or more of volatile or nonvolatile memorydevices such as RAM, flash memory, hard drives, solid state devices,CDs, DVDs, optical memory, magnetic memory or other circuit readablemediums or media upon which computer executable instructions and/or datamay be stored.

Circuit executable instructions, may include instructions in any of aplurality of programming languages and formats including, withoutlimitation, routines, subroutines, programs, threads of execution,objects, scripts, methodologies and functions which carry out theactions such as those described herein. Structures for the controlcircuits may include, correspond to and utilize the principles describedin the textbook entitled Microprocessor Architecture, Programming, andApplications with the 8085 by Ramesh S. Gaonker (Prentice Hall, 2002),which is incorporated herein by reference in its entirety. Of course itshould be understood that these control circuit structures are exemplaryand in other arrangements, other circuit structures for storing,processing, resolving and outputting information may be used.

In the exemplary arrangement, the at least one control circuit 142 is inoperative connection through suitable interfaces with at least onesensor such as sensors 134, 136 and 138. The at least one controlcircuit is also in operative connection with the variable flow ratedischarge pump 120. Further in some exemplary arrangements, the at leastone control circuit may also be in operative connection with otherdevices such as motor 86, pump 108, regulator 132, air pressure source128, the fluid control valves and other devices.

The exemplary at least one control circuit is operative to receive dataand control such devices in accordance with circuit executableinstructions stored in the data store 146. In the exemplary arrangement,the fluid level 147 in the fluid damping reservoir is a property thatcorresponds to pressure in the centrate discharge tube 102. In oneexemplary implementation which does not utilize air line 143, the factthat the pressure in the centrate discharge tube is indicative of thepressure in the top portion 104 of the core and the nature of thepressure in the separation chamber adjacent to the seal 106 is utilizedto control the operation of the discharge pump and other components. Aspreviously discussed, it is desirable to maintain a positive pressureabove atmospheric pressure and a pocket of air adjacent to the at leastone seal within the separation chamber to avoid the introduction ofcontaminants into the separation chamber which could result fromnegative pressure. However, if the fluid level becomes too high withinthe separation chamber, the pressure and the suspension material beingprocessed may overflow the seal which may result in potentialcontamination and undesirable exposure and loss of processed material.This may result from conditions where the back pressure on the centrateline which is in connection with the outlet from the centripetal pump istoo high.

In the exemplary arrangement the bowl speed produces a correspondingpumping force and a pump output pressure level of the centripetal pump.This pump output pressure level of the centripetal pump varies with therotational speed of the bowl and the core. The exemplary arrangementwithout the use of air line 143 provides for a back pressure to becontrolled on the centrate outlet tube. Back pressure is provided bycontrolling the speed of a motor operating the pump 120 and the liquidlevel 147 in the pressure damping reservoir. The back pressure ismaintained so as to be less than the pump output pressure level (so thatthe centripetal pump may deliver centrate out of the separation chamber)but is maintained at a positive pressure above atmospheric so as toassure that contaminants will not infiltrate into the separation chamberpast the seal, and so that air at elevated pressure is maintained in theinterior of the separation chamber adjacent to the seal so as to isolatethe seal from the components of the suspension being processed.

In the exemplary arrangement the elevated pressure applied to the topport 126 of the pressure damping reservoir is maintained by theregulator 132. Further by the at least one control circuit 142controlling the speed of pump 120 to maintain the liquid level 147between the upper liquid level as sensed by the sensor 134 and the lowerliquid level 136, centrate flow out of the separation chamber iscontrolled so that the pressure of the top area of the separationchamber is maintained at a desired constant value and the centrate doesnot contact or overflow the seal.

In an alternate arrangement with the use of air line 143, the positivepressure level of the regulator acts on both the fluid in the reservoir122 and the area of the separation chamber above the centripetal pumpinlet. Because the positive pressure level of air applied in bothlocations is the same, the back pressure on the centrate discharge line(which is the pressure applied above the fluid in the reservoir) isvirtually always the same as the pressure in the air pocket at the topof the separation chamber. This enables the centripetal pump to operatewithout any net effect from either pressure.

In this exemplary arrangement the pump 120 and other system componentsare controlled responsive to the at least one control circuit 142 toassure that there is an adequate volume of air within the interior ofthe reservoir 122 at all times during centrate production. This assuresthat the reservoir provides the desired damping effect on changes incentrate discharge line pressure that might otherwise be caused by thepumping action of pump 120. This is done by maintaining the liquid inthe reservoir 122 at no higher than the upper liquid level detected bysensor 134. Further, the liquid level in the reservoir is controlled tobe maintained above the lower liquid level as sensed by sensor 136. Thisassures that the centripetal pump is not pumping air and aerating thecentrate.

In the exemplary arrangement the centrate flow out of the separationchamber is controlled through operation of the at least one controlcircuit. The exemplary control circuitry may operate the system duringprocessing conditions to maintain the incoming flow of cell suspensionby pump 108 to the separation chamber 90 at a generally constant rate,while the separation process is occurring with the motor 86 operating tomaintain the constant bowl speed to achieve the separation of thecentrate and the cell concentrate. The exemplary arrangement furtheroperates to maintain an ideally constant back pressure on the centratedischarge line from the centripetal pump while maintaining air in theseparation chamber above the level of the lower side of the air pocketto isolate the at least one seal 106 from the centrate and concentratematerial being processed.

In an exemplary arrangement, the pressure maintained through operationof the regulator in the pressure damping reservoir is set atapproximately 2 kpa (0.29 psi) above atmospheric. In the exemplarysystem this pressure has been found to be suitable to assure that theseal integrity and isolation is maintained during all stages of cellsuspension processing. Of course it should be understood that this valueis exemplary and in other arrangements, other pressure values andpressure damping reservoir configurations, sensors and other featuresmay be utilized.

FIG. 20 shows schematically exemplary logic executed through operationof the at least one control circuit 142 in connection with maintainingthe desired pressure level in the centrate discharge tube and within thetop portion of the separation chamber. It should be understood that thecontrol circuits in some exemplary arrangements may perform numerousadditional or different functions other than those represented. Thesefunctions may include the overall control of the different processes andsteps for operation of the centrifuge in addition to the describedpressure control function. As represented in FIG. 20, in an initialsubroutine step 148, the at least one control circuit 142 is operativeto make a determination on whether the centrifuge operation is currentlyin a mode where centrate is being discharged from the separationchamber. If so, the at least one control circuit is operative to causethe centrate discharge pump 120 to operate to discharge centratedelivered through the centrate discharge line 118. This may be done bycausing operation of a motor of the pump. In the exemplary arrangement,the flow rate of the pump 120 may be a set value initially oralternatively may be varied depending on particular operating conditionsthat are determined through control circuit operation during theprocess. The operation of the centrate discharge pump is represented bya step 150.

The at least one control circuit is then operative to determine in astep 152 whether liquid is sensed at the high level of the high liquidlevel sensor 138. If so, this represents an undesirable condition. Ifliquid is sensed at the level of the sensor 138, the control circuitthen operates to take steps to address the condition. This may includeoperating the pump 120 to increase its flow rate and making subsequentdeterminations if the level drops within a period of time while thecentrifuge continues to operate. Alternatively or in addition, the atleast one control circuit may decrease the speed of pump 108 to reducethe flow of incoming material. If such action does not cause the levelto drop within a set period of time, additional steps are taken. Suchsteps may also include slowing or stopping rotation of the bowl 182.Such actions may also include stopping the operation of pump 108 so asto avoid the introduction of more suspension material into theseparation chamber. These steps which are generally referred to asshutting down normal operation of the system are represented by a step154.

If liquid is not sensed at the level of the high level sensor 138, theat least one control circuit is next operative to determine if liquid issensed at the upper liquid level of sensor 134. This is represented bystep 156. If liquid is sensed at the upper liquid level sensor, the atleast one circuit operates responsive to its stored instructions toincrease the speed and therefore the flow rate of discharge pump 120.This is done in an exemplary arrangement by increasing the speed of themotor that is a part of the pump. This is represented by a step 158.Increasing the flow rate of the pump causes the liquid level 147 in thepressure damping reservoir to begin to drop as more liquid is moved bythe pump 120.

If in step 156 liquid is not sensed at the upper liquid level of sensor134, the at least one control circuit then operates to make adetermination as to whether liquid is not sensed at the lower liquidlevel of sensor 136. This is represented by step 160. If the liquidlevel is not at the level of the sensor 136, the control circuitryoperates in accordance with its programming to control the pump 120 todecrease its flow rate. This is done in an exemplary arrangement byslowing the speed of the motor. This is represented by a step 162. Inthe exemplary arrangement, slowing the flow rate of the pump 120 causesthe liquid level 147 to begin rising in the pressure damping reservoir.In some exemplary arrangements if the level does not rise within thereservoir within a given time, the control circuitry may operate inaccordance with its programming to cause additional actions, such asactions associated with shut down step 154 previously discussed. Thecontrol circuitry of exemplary arrangements may operate to change thepumping rate of pump 120 to maintain the level 147 within the pressuredamping reservoir at a generally constant level between the levels ofsensors 134 and 136 during centrate production.

In the exemplary arrangement, maintaining the generally constantelevated pressure of sterile air over the liquid in the pressure dampingreservoir helps to assure that a similar elevated pressure isconsistently maintained in the centrate outlet line and at the sealwithin the separation chamber. Further in the exemplary arrangements,the pressure is enabled to be controlled at the desired level duringdifferent operating conditions of the centrifuge during which the bowlrotates at different speeds. This includes, for example, conditionsduring which the separation chamber is initially filled at a relativelyhigh rate through the introduction of cell suspension and during whichthe centrifuge rotates at a relatively lower speed. Pressure can also bemaintained during the subsequent condition of final fill in which theflow rate of cell suspension into the separation chamber occurs at aslower rate and during which the rotational speed of the bowl isincreased to a higher rotational speed. Further, positive pressure ismaintained as previously discussed during the feeding of the suspensioninto the bowl and during discharge of the centrate from the separationchamber. Further in exemplary arrangements, the at least one controlcircuit may operate to also maintain the positive pressure during thetime period that the concentrate is removed by having it pumped out ofthe separation chamber. Maintaining positive pressure within theseparation chamber during all of these conditions reduces the risk ofcontamination and other undesirable conditions which otherwise mightarise due to negative pressure (below atmospheric pressure) conditions.

Of course it should be understood that the features, components,structures and control methodologies are exemplary, and in otherarrangements other approaches may be used. Further, although theexemplary arrangement includes a system which operates in a batch moderather than a mode in which both centrate and concentrate arecontinuously processed, the principles hereof may also be applied tosuch other types of systems.

While the pressure damping reservoir is useful in exemplary arrangementsto help assure that a desired pressure level is maintained in the outlettube and the separation chamber, other approaches may also be utilizedin other arrangements. For example, in some arrangements pressure may bedirectly sensed and/or applied in the outlet tube, the separationchamber or in other locations which correspond to the pressure in theseparation chamber. In some arrangements, the flow rate of the dischargepump may be controlled so as to maintain the suitable pressure level. Instill other arrangements, exemplary control circuits may be operative tocontrol both the discharge pump and a pump that feeds suspension intothe core and/or suitable valving or other flow control devices so as tomaintain suitable pressure levels. Such alternative approaches may bedesirable depending on the particular centrifuge device being utilizedand the type of material being processed.

FIG. 21 shows schematically an alternative centrifuge system 170particularly configured to separate cells in a cell culture batch intocell centrate and cell concentrate on a continuous or semi-continuousbasis. The exemplary system shows a rigid centrifuge bowl 172 that isrotatable about an axis 174. The bowl includes a cavity 176 configuredfor releasably receiving a single use structure 178 therein. The rigidbowl includes an upper opening 180. An annular securing ring or othersecuring structure schematically represented 182 enables releasablysecuring the single use structure 178 within the bowl cavity.

The exemplary single use structure 178 of this example arrangementincludes a central axially extending feed tube 184. As later discussedthe feed tube is used to deliver the cell culture batch material intothe interior area 186 of the single use structure 178. The feed tube 184extends from an upper portion at a first axial end 188 of the single usedevice, to an opening 190 which is in the interior area at a lowerportion at a second axial end 192. The single use structure 178 includesa substantially disc shape portion 194 adjacent the first axial end.Exemplary disc shape portion 194 is generally rigid which means that itis rigid or semi-rigid, and includes an annular outer periphery 196. Theannular outer periphery is configured to engage the upper annularbounding wall 198 of the centrifuge bowl cavity 176. The annular outerperiphery of the disc shape portion 194 is configured to engage therigid bowl 172 so that the single use structure is rotated therewith.

The exemplary single use structure 178 further includes a hollow rigidor at least semi-rigid cylindrical core 200. Core 200 is operativelyengaged with the disc shape portion 194 and is rotatable therewith. Thecore 200 is axially aligned with the disc shape portion and extendsaxially intermediate of the upper portion and the lower portion of thesingle use structure. The core 200 includes an upper opening 202 and alower opening 204 through which the feed tube 184 extends.

Disc shape portion 194 includes a substantially circular centratecentripetal pump chamber 206. A centrate centripetal pump 208 ispositioned in chamber 206. A substantially annular centrate opening 210is in fluid connection with the centrate pump chamber 206. Bysubstantially annular it is meant that the opening may be comprised ofdiscrete openings in an annular arrangement and/or a continuous opening.Centrate centripetal pump 208 is in fluid connection with a centratedischarge tube 212. Centrate discharge tube 212 extends in coaxialsurrounding relation of feed tube 184. The centrate discharged passesthrough the substantially annular opening at the periphery of thecentrate centripetal pump and through the annular space in the centratedischarge tube 212 on the outside of the feed tube.

Disc shape portion 194 further includes a concentrate centripetal pumpchamber 214. Concentrate centripetal pump chamber 214 is a substantiallycircular chamber that is positioned above centrate centripetal pumpchamber 206. Concentrate centripetal pump chamber 214 has a concentratecentripetal pump 216 positioned therein. The concentrate centripetalpump is in fluid connection with a concentrate discharge tube 220. Theconcentrate discharge tube 220 extends in annular surrounding relationof the centrate discharge tube 212. Concentrate passes through thesubstantially annular opening at the periphery of the concentratecentripetal pump and through the annular space in the concentratedischarge tube 220 on the outside of the centrate discharge tube.

A substantially annular concentrate opening 218 is in fluid connectionwith the concentrate pump chamber 214. In the exemplary arrangement thesubstantially annular concentrate opening and the substantially annularcentrate opening are concentric coaxial openings with the concentrateopening disposed radially outward of the centrate opening. Of coursethis arrangement is exemplary and in other arrangements other approachesand configurations may be used.

The exemplary single use structure 178 further includes a flexible outerwall 222. Flexible outer wall 222 is a fluid tight wall that in theoperative position of the exemplary single use structure 178 extends inoperatively supported engagement with the wall bounding the rigid bowlcavity 176. In the exemplary arrangement the flexible outer wall 222 isoperatively engaged in fluid tight connection with the disc shapeportion 194. The flexible outer wall has an internal truncated coneshape with a smaller inside radius adjacent to the lower portion of thesingle use structure which is adjacent to the second axial end 192.

The exemplary flexible outer wall 222 extends in surrounding relation ofat least a portion of the core 200. Wall 222 further bounds an annularseparation chamber 224. The separation chamber 224 extends radiallybetween the outer wall of core 200 and the flexible outer wall 222. Thesubstantially annular concentrate opening 218 and the substantiallyannular centrate opening 210 are each in fluid communication with theseparation chamber 224.

In the exemplary arrangement the flexible outer wall 222 has a texturedouter surface 226. The textured outer surface is configured to enableair to pass out of the space between the surface bounding the cavity ofthe rigid bowl 172 and the flexible outer wall 222. In an exemplaryarrangement the textured outer surface may include substantially theentire area of the flexible outer wall that contacts the rigid bowl. Inexemplary arrangements the textured outer surface may include one ormore patterns of outward extending projections or dimples 228 withspaces or recesses therebetween to facilitate the passage of air. Airmay pass out of the bowl cavity 176 when the single use structure 178 ispositioned therein either through the upper opening 180 or through alower opening 230. In exemplary arrangements the projections may becomprised of resilient deformable material that can decrease in heightresponsive to force of the liner against the rigid wall of the bowl. Thetextured outer surface 226 of the flexible outer wall 222 reduces therisk that air pockets will be trapped between the rigid bowl of thecentrifuge and the single use structure. Such air pockets may causeirregularities in wall contour which may create imbalances and/or changethe contour of the separation chamber in a way that adversely impactsthe separation processes. Of course it should be understood that the airrelease structures described are exemplary and other arrangements otherair release structures may be used.

The exemplary single use structure shown in FIG. 21 further includes alower rigid or semi-rigid disc shape portion 232. The rigid orsemi-rigid material operates to maintain its shape during operation. Inthe exemplary arrangement lower disc shape portion 232 has a conicalshape and is in operative attached connection with the lower end of core200 by vertically extending wall portions or other structures. Aplurality of angularly spaced fluid passages 234 extend between theupper surface of disc shape portion 232 and the radially outward lowerportion of the core. Fluid passages 232 extend radially outward andupwardly relative to the bottom of the second axial end 192, and enablethe cells in the cell culture batch material that enters the interiorarea 186 through the opening 190 in feed tube 184, to pass radiallyoutwardly and upwardly into the separation chamber 224.

In the exemplary arrangement the flexible outer wall 222 extends belowthe lower disc shape portion 232 at the second axial end 192 of thesingle use structure. The flexible outer wall 222 extends intermediateof the lower disc shape portion 232 and the wall surface of the rigidbowl 172 which bounds the cavity in which the single use structure isposition.

In the exemplary arrangement the feed tube 184, centrate discharge tube212 and concentrate discharge tube 220, as well as with centratecentripetal pump 208 and concentrate centripetal pump 216 remainstationary while the centrifuge bowl 172 and the upper disc shapeportion 194, lower disc shape portion 232 and flexible outer wall 222rotate relative thereto with the bowl. At least one annular resilientseal 236 extends in sealing engagement operatively between the outersurface of the concentrate discharge tube 220 and the upper disc shapeportion 194. The at least one seal 236 maintains an air tight seal in amanner like that previously discussed, so that an air pocket may bemaintained in the interior area 186 during cell processing so as toisolate the seal from the cell culture batch material being processed.The air pocket maintained within the interior area of the single usestructure is configured such that the centrate centripetal pump 208 andthe concentrate centripetal pump 216 remain in fluid communication withthe cell culture batch material. In a manner like that previouslydiscussed, a positive pressure may be maintained within the interiorarea so as to assure that an air pocket is present to adequately isolatethe at least one seal 236 from the cell culture batch material beingprocessed. Alternatively, other approaches may be utilized for purposesof maintaining the isolation of the seal from the material beingprocessed.

The exemplary system 170 operates in a manner like that previouslydiscussed. Cells in a cell culture batch material are introduced to theinterior area 186 of the single use structure 178 through the feed tube184. The cells enter the interior area 186 through the feed tube opening190 at the lower axial end of the single use structure. Centrifugalforces cause the cells to move outwardly through the openings 234 andinto the separation chamber 224. The outwardly and upwardly taperedouter wall 222 causes the cells or cell material containing cellconcentrate to collect adjacent to the radially outward and upper areaof the separation chamber 224. The generally cell free centrate collectsin the separation chamber radially inward adjacent to the outer wall ofthe core 200.

In the exemplary arrangement the cell centrate passes upwardly throughthe substantially annular centrate opening into the centrate pumpchamber. The centrate passes inward through the substantially annularopening of the centrate centripetal pump and then upwardly through thecentrate discharge tube 212. At the same time the cell concentratepasses through the substantially annular concentrate opening 218 andinto the concentrate centripetal pump chamber 214. The cell concentratepasses inwardly through the substantially annular opening of theconcentrate centripetal pump 216 and then upwardly through theconcentrate discharge tube 220. This exemplary configuration enables theexemplary system 170 operate on a continuous or semi-continuous basis.The operation of the system 170 may be controlled in a manner like thatlater discussed so as to facilitate reliable extended operation of thesystem and delivery of the desired cell concentrate and generally cellfree centrate in separate output fluid streams.

FIG. 22 shows an alternative centrifuge system generally indicated 238.System 238 has a single use structure 240. Single use structure 240 issimilar in most respects the single use structure 178 previouslydescribed. Some of the structures and features of single use structure240 that are generally the same as those described in connection withsingle use structure 178 are labeled with the same reference numerals asthose used to describe single use structure 178.

Single use structure 240 differs from single use structure 178 in thatit includes a rigid or semi-rigid lower disc shape portion 242. Lowerdisc shape portion 242 is a generally cone shape structure that is inoperative connection with the lower end of core 200. A plurality ofradially outward and upward extending fluid passages 244 extend betweenthe lower end of the core 200 and the lower disc shape portion 242. Theexemplary lower disc shape portion 242 further includes a plurality ofangularly spaced radially extending vanes 246. A fluid passage extendsradially outward between each immediately angularly adjacent pair ofvanes 246. In this exemplary arrangement the vanes 246 extend upwardlyfrom a bottom portion of disc shape portion 242 and at least some are inoperative engagement with the core at radially outer portions thereof.In the exemplary arrangement the vanes 246 accelerate the cell culturebatch to facilitate movement and separation within the interior area ofthe single use structure.

An alternative exemplary arrangement of a centrifuge system 248 is shownin FIG. 23. This exemplary arrangement includes a single use structure250. Single use structure 250 is similar in many respects to thepreviously described single use structure 178. Some of the structuresand features that are like those in the previously described single usestructure 178 are labeled on single use structure 250 with the samereference numbers.

The exemplary single use structure 250 differs from single use structure178 in that it includes a lower disc shape portion 252. Lower disc shapeportion 252 is a rigid or semi-rigid cone shape structure that is inoperatively attached connection with the core 200 via wall portions orother suitable structures. Lower disc shape portion 252 includes aplurality of angularly spaced radially outward extending acceleratorvanes 254. Accelerator vanes 254 extend downwardly from a lower conicalside of disc shape portion 252. Each immediately angularly adjacent pairof vanes 254 has a fluid passage extending therebetween. In thisexemplary arrangement the flexible outer wall 222 extends inintermediate relation between the lower ends of the vanes 254 and thewall of the rigid bowl 172 bounding the cavity 176. This exemplaryconfiguration provides a submerged accelerator which is operative toaccelerate the cell culture batch material so as to facilitate theseparation thereof within the interior area of the single use structure.Of course it should be understood that the single use structuralfeatures described herein may be combined in different arrangements soas to facilitate the separation of different types of materials andsubstances with different properties and to achieve desired output fluidstreams.

FIG. 26 shows an alternative single use structure 304. Single usestructure 304 is similar to single use structure 178 previouslydescribed except as otherwise mentioned herein. Elements that are thesame as those in single use structure 178 have been designated using thesame reference numbers in FIG. 26.

Single use structure 304 includes a continuous annular concentrate dam306. Concentrate dam 306 extends downward in the separation chamber 224and is disposed radially inward of the substantially annular concentrateopening 218. The exemplary annular concentrate dam shown incross-section extends downward below the concentrate opening and inaxial cross-section includes a tapered outward surface 308 that extendsoutwardly and toward opening 218.

Single use structure 304 further includes a continuous annular centratedam 310. Centrate dam 310 extends downward in the separation chamber 224below the substantially annular centrate opening 210. Centrate dam 310is disposed radially outward from the centrate opening 210. In theexemplary arrangement the downward distance that the concentrate dam 306and the centrate dam 310 extend in the separation chamber 224 issubstantially the same. However in other exemplary arrangements otherconfigurations may be used. Also in other example arrangements acentrifuge structure may include a concentrate dam or a centrate dam,but not both.

An annular recess 312 extends in the separation chamber radially betweenthe centrate dam and the concentrate dam. The exemplary annular recessextends upward between the centrate and concentrate dams so as to forman annular pocket therebetween.

In exemplary arrangements the concentrate dam 306 helps to assure thatprimarily cellular material or other solid material to be separated canpass outwardly along the upper portion bounding the separation chamber224 to reach the concentrate opening 218 and the concentrate centripetalpump chamber 214. The centrate dam 310 further helps to assure thatprimarily cell free centrate material is enabled to pass along the uppersurface bounding the separation chamber 224 and into the substantiallyannular centrate opening 210 to reach the centrate pump chamber 206. Itshould be understood the numerous different configurations ofconcentrate and centrate dams may be utilized in different examplearrangements depending on the nature of the material being processed andthe requirements for handling such materials.

FIG. 24 is a schematic view of an exemplary control system for providinggenerally continuous processing of a cell culture material to producestreams of generally cell free centrate and cell concentrate. In theexemplary arrangement the centrifuge system 170 previously discussed isshown. However it should be understood that the exemplary systemfeatures may be used with numerous different types of materials andcentrifuge systems and structures such as those discussed herein.

In the exemplary arrangement shown, the centrifuge bowl 172 is rotatedat a selected speed about axis 174 by a motor 256. The feed tube 184 isin operative connection with a cell culture feed line 258 through whichthe cell culture batch material is received. The feed line is inoperative connection with a feed pump 260. In exemplary arrangement feedpump 260 may be a peristaltic pump or other suitable pump for deliveringcell culture into the single use structure at a selected flow rate.

The centrate discharge tube 212 is in fluid connection with a centratedischarge line 262. A centrate optical density sensor 264 is inoperative connection with an interior area of the centrate dischargeline 262. In the exemplary arrangement the centrate optical densitysensor is an optical sensor that is operative to determine the densityof cells currently in the centrate passing from the single usestructure. This is accomplished in the exemplary arrangement bymeasuring the reduction in intensity of light output by an emitter thatis received by a receiver disposed from the emitter and which has atleast a portion of the centrate flow passing there-between. The amountof light from the emitter that is received by the receiver decreaseswith the increasing density of cells in the centrate. Of course this isonly one example of a sensor that may be utilized for purposes ofdetermining the density or amount of cells present in the centrate, andin other arrangement other types of sensors may be used. For example,the light may be near infrared or other visible or non-visible light. Inother sensing arrangements other forms of electromagnetic, sonic orother types of signals may be used for sensing. The centrate dischargeline is further in operative connection with a centrate pump 266. In theexemplary arrangement the centrate pump may comprise a peristaltic pumpor other variable rate pump suitable for pumping the centrate material.

In the exemplary arrangement the concentrate discharge tube 220 is inoperative connection with a concentrate discharge line 268. Aconcentrate optical density sensor 270 is in operative connection withat least a portion of the interior area of the concentrate dischargeline 268. The exemplary concentrate optical density sensor may operatein a manner like the centrate optical density sensor previouslydiscussed. Of course it should be understood that the concentrateoptical density sensor may include different structures or properties,and that different types of cell density sensors may be used in otherexemplary arrangements. The concentrate discharge line 268 is inoperative connection with a concentrate pump 272. In the exemplaryarrangement the concentrate pump 272 may include a peristaltic pump orother variable rate pump suitable for pumping the concentrate withoutcausing damage thereto. Of course it should be understood that thesestructures and components are exemplary and alternative systems mayinclude different or additional components.

The exemplary control system includes control circuitry 274 which isalternatively referred to herein as a controller. In exemplaryarrangements the control circuitry may include one or more processorsschematically indicated 276. The control circuitry may also include oneor more data stores schematically indicated 278. The one or more datastores may include one or more types of tangible mediums which holdcircuit executable instructions and data which when executed by thecontroller cause the controller to carry out operations such as thoselater discussed herein. Such mediums may include for example,solid-state memory, magnetic memory, optical memory or other suitablenon-transitory medium for holding circuit executable instructions and/ordata. The control circuitry may include structures like those previouslydiscussed.

The operations carried out by the exemplary controller 274 will now bedescribed in connection with the schematic representation of a logicflow shown in FIG. 25. In the exemplary arrangement the controller 274is operative to control the operation of the components in the system soas to maintain the delivery of concurrent output flows of generally cellfree centrate and cell concentrate. This is accomplished using theoptical density sensors in the respective centrate and concentrateoutlet lines to detect the cell density (or turbidity) of the outputfeeds and to adjust the operation of the system components so as tomaintain the output within desired ranges.

In the use of the exemplary control system, the cell concentration ofcells in the cell culture material to be processed is measuredseparately prior to initiating the operation of the system. The desiredaxial rotation speed of the centrifuge is determined as is a speed foroperation of the feed pump 260. In the exemplary arrangement therotational speed of the centrifuge and the feed rate of the cellmaterial by the feed pump are generally maintained by the controller asconstant set values. Of course in other arrangements and systemsalternative approaches may be used in which the speeds and feed ratesmay be adjusted by the controller during cell processing.

In the exemplary arrangement, based on the determined cellconcentration, the discharge rate (flow rate) of the externalconcentrate pump 272 is set at an initial value which is referred toherein as a “prime value.” Also preset in the exemplary arrangement is a“prime duration” which corresponds to a time period during which theexternal concentrate pump 272 will operate initially at the prime value.This duration allows the single use structure 178 to partially fill.Also in the exemplary system a “base speed” is set for the concentratepump based on the cell density as well as the feed rate from the feedpump 260. The base speed of the concentrate pump is a speed (whichcorresponds to flow rate) at which the concentrate pump will operatesubsequent to the prime duration. In the exemplary arrangement the setbase speed is generally expected to correspond to a concentrate pumpspeed which will produce centrate with the cell density below a desiredset limit and cell concentrate with the cell density generally above afurther desired set limit. The set values and limits are received by thecontroller in response to inputs through suitable input devices andstored in the at least one data store.

In the exemplary logic flow represented in FIG. 25, the operation of theconcentrate pump 272 at the initial prime speed is represented by step280. A determination is made at a step 282 by the controller as towhether the concentrate pump has operated at the prime speed for thetime period corresponding to the prime duration which is operative to atleast partially fill the single use structure 178.

Once the concentrate pump has operated at the prime speed for the primeduration, the controller causes the concentrate pump speed to thenincrease to the base speed as represented by a step 284. The controller274 operates to monitor the cell density in the centrate as detected bysensor 264. The controller operates to determine if the optical densityis higher than the desired set point as represented by step 286. If theoptical density of the centrate is not higher than the set point, thenthe centrate is sufficiently clear of cells or cell material such thatthis measurement does not cause a change by the controller in theoperating speed of the concentrate pump, and the logic returns to step284.

If in step 286 the optical density of the centrate is determined to behigher than the set point, then the logic proceeds to a step 288. Instep 288 the controller operates to increase the speed of theconcentrate pump by a set incremental step amount. This speed stepincrease is intended to generally cause the optical density of thecentrate to clear as a result of reducing the number of cells therein.

After the speed of the concentrate pump 272 is increased in step 288 thecontroller then operates responsive to the sensor 264 to determine in astep 290 if the optical density of the centrate is still above the setpoint a set time after the incremental increase in the speed (flow) ofthe concentrate pump. If it is, then the controller continues to monitorthe optical density of the centrate until it is not higher than the setpoint. In the exemplary arrangement the instructions include a set timeperiod during which the centrate optical density must not be higher thanthe set point before the concentrate pump speed controller determinesthat the adjustment to the base speed is sufficient to maintain theoptical density of the centrate at a level that is at or below thedesired set point. Step 292 is representative of the controller making adetermination that the increased concentrate pump speed has maintainedthe optical density of the centrate at or below the set point for thestored set time period value which corresponds to consistently producingan outflow of sufficiently cell free centrate or reaching the programmedwait time. Responsive to producing the sufficiently cell free centratefor the desired duration or reaching the programmed wait time, thecontroller next operates in a step 294 to cause the base speed value ofthe concentrate pump to be adjusted to correspond to the increased basespeed. The controller sets the new base speed and the logic returns tothe step 284. It should be noted that if the centrate optical density isstill above the set point as determined in step 286, the concentratepump speed will again be adjusted.

The exemplary controller also concurrently monitors the optical densityof the cells in the output concentrate flow. This is done by monitoringthe optical density as detected by sensor 270. As represented by step296 the controller operates to determine if the optical density in theconcentrate is lower than a desired setpoint. If the concentrate opticaldensity is detected at or above the desired set point value that isstored in the data store, then the concentration of cells in theconcentrate output flow is at or above the desired level, and the logicreturns to the step 284. However if the optical density of theconcentrate is below the desired set point, meaning that the level ofcells in the concentrate is less than desired, the controller moves to astep 298. In step 298 the speed of the concentrate pump is reduced by apredetermined incremental step amount. Reducing the speed of theconcentrate pump will reduce output flow rate, generally increase theamount of cells in the concentrate output flow and therefore increasethe optical density of the concentrate output flow.

The controller then operates the concentrate pump 272 at the new reducedspeed as represented in a step 300. As represented in the step 302 thecontroller operates the concentrate pump at this reduced speed for a settime period corresponding to a set value stored in the data store sothat the concentration of cells in the output concentrate flow mayincrease before a determination is made as to whether the speed decreaseis sufficient. Once the time period is determined to have passed in thestep 302, the controller returns to the step 284 from which the logicflow is then repeated to determine if further speed adjustments areneeded.

Of course it should be understood that this schematic simplified logicflow is exemplary and in other arrangements a different logic flowand/or additional operating parameters of system components may bemonitored and adjusted for purposes of achieving the desired output flowof centrate and concentrate. For example in other exemplary arrangementsthe speed of the centrate discharge pump, and thus the centratedischarge flow, may be varied by the controller responsive at least inpart to the optical density as detected by the centrate optical densitysensor which corresponds to the level of cells in the centrate. Forexample, the controller may operate to reduce the flow rate of thecentrate pump if the level of cells in the centrate is detected as abovea set limit. This may be done by the controller as an alternative to orin combination with controlling the concentrate discharge flow rate. Thecontroller may vary the centrate flow as appropriate to assure that thelevel of cells in the centrate is maintained below set limits or withina set range.

Alternatively or in addition the controller may also control the flowrate of cell suspension entering the single use structure. This may bedone in conjunction with varying the flow rates of centrate andconcentrate from the single use structure, to maintain the level ofcells in the centrate and concentrate within the programmed set limitsthat are stored in memory associated with the controller. Additionallythe controller may also operate in accordance with its programming tovary other process parameters such as variation of bowl rotationalspeed, the introduction of dilutant and dilutant introduction rates aswell as other process parameters to maintain the centrate andconcentrate properties within programmed limits and desired processrates. Further in other exemplary arrangements other properties orparameters may be monitored and adjusted by the control system forpurposes of achieving the desired products.

FIG. 27 shows a cross-sectional view of a further alternative single usecentrifuge structure 314. Single use structure 314 is generally similarto single use structure 178 previously discussed except as specificallymentioned. Single use structure 314 includes elements that are operativeto help assure that the air/liquid interface of the air pocket thatextends in the single use structure and that isolates the seal 236 fromthe material that is being processed is more stably maintained at adesired radial location.

In the single use structure 314 the centrate pump 208 is positioned in acentrate pump chamber 316. Centrate pump chamber 316 is boundedvertically at the bottom by a circular lower centrate centripetal pumpchamber surface 318. Centrate pump chamber 316 is bounded vertically atthe upper side by a circular upper centrate centripetal pump chambersurface 320.

Lower centrate pump chamber surface 318 extends radially outward from alower centrate centripetal pump chamber opening 322. In the exemplaryarrangement the lower centrate centripetal pump chamber opening 322extends through a circular top of the core 200 and corresponds to upperopening 202 previously discussed. The feed tube 184 extends through thelower centrate centripetal pump chamber opening.

Upper centrate centripetal pump chamber surface 320 extends radiallyoutward from a circular upper centrate centripetal pump chamber opening324. The feed tube 184 and the centrate discharge tube 212 extendaxially through the upper centrate centripetal pump chamber opening.

A plurality of angularly spaced upward extending lower centrate chambervanes 326 extend on the lower centrate centripetal pump chamber surface318. Each of the lower centrate chamber vanes 326 extend radiallyoutward beginning from the lower centrate centripetal pump chamberopening 322. The lower centrate chamber vanes 326 which are shown ingreater detail in FIG. 28 extend radially outward from the axis ofrotation 174 a lower centrate vane distance V. In the exemplaryarrangement the lower centrate chamber vanes 326 extend upward in acircular recess on the lower centrate centripetal pump chamber surface318. However it should be understood that this arrangement is exemplaryand other arrangements may be used; for example the radial length of thevanes, vane height, and the depth and diameter of the recess may bevaried to achieve desired fluid pressure properties.

A plurality of angularly spaced downward extending upper centratechamber vanes 328 extend from upper centrate centripetal pump chambersurface 320. Each of the upper centrate chamber vanes 328 extendradially outward beginning from the upper centrate centripetal pumpchamber opening 324. The upper centrate chamber vanes extend radiallyoutward from the axis of rotation 174 an upper centrate vane distance.In the exemplary arrangement the upper centrate vane distancesubstantially corresponds to the lower centrate vane distance V. In theexemplary arrangement the upper centrate chamber vanes extend downwardin a circular recess on the upper centrate centripetal pump chambersurface that has a configuration like that shown for the lower centratechamber vanes in FIG. 28, but in an inverted orientation.

In the exemplary arrangement shown the centrate centripetal pump 208includes a substantially annular centrate centripetal pump opening 330.The substantially annular centrate centripetal pump opening 330 isdisposed radially outward from the axis of rotation 174, a centrate pumpopening distance. The centrate pump opening distance at which thecentrate centripetal pump opening 330 is positioned, is a greater radialdistance than the lower centrate vane distance and the upper centratevane distance for reasons that are later discussed.

In the exemplary arrangement of the single use structure 314 theconcentrate centripetal pump 216 is positioned in a concentrate pumpchamber 332. Concentrate pump chamber 332 is bounded vertically at alower side by a circular lower concentrate centripetal pump chambersurface 334. Concentrate pump chamber 332 is bounded vertically at anupper side by a circular upper concentrate centripetal pump chambersurface 336.

The lower concentrate centripetal pump chamber surface 334 extendsradially outward from a lower concentrate centripetal pump chamberopening 338. In the exemplary arrangement the lower concentratecentripetal pump chamber opening corresponds in size to and iscontinuous with the upper centrate centripetal pump chamber opening 324.The feed tube 184 and the centrate discharge tube 212 extend through thelower concentrate centripetal pump chamber opening 338.

A plurality of angularly spaced upward extending lower concentratechamber vanes 340 extend on lower concentrate centripetal pump chambersurface 334. The lower concentrate chamber vanes 334 extend radiallyoutward beginning from the lower concentrate centripetal pump chamberopening 338. The lower concentrate chamber vanes 334 extend radiallyoutward from the axis of rotation a lower concentrate vane distance. Inthe exemplary arrangement the lower concentrate chamber vanes 334 extendon a circular recess portion of the lower concentrate centripetal pumpchamber surface similar to the upper and lower centrate chamber vanespreviously discussed. Of course it should be understood that thisconfiguration is exemplary.

Upper concentrate centripetal pump chamber surface 336 extends radiallyoutward from an upper concentrate centripetal pump chamber opening 342.The feed tube 184, the centrate discharge tube 212 and the concentratedischarge tube 220 coaxially extend through the upper concentratecentripetal pump chamber opening 342. A plurality of angularly spacedupper concentrate chamber vanes 344 extend downward from surface 336.The upper concentrate chamber vanes extend radially outward from theupper concentrate centripetal pump chamber opening 342 an upperconcentrate vane distance. The upper concentrate chamber vanes extend inan upward extending circular recess in the upper concentrate centripetalpump chamber surface. In the exemplary arrangement the upper concentratechamber vanes are configured in a manner similar to the lowerconcentrate chamber vanes and the upper and lower centrate chamber vanespreviously discussed. Of course it should be understood that thisapproach is exemplary and in other arrangements other approaches may beused.

Concentrate centripetal pump 216 includes a substantially annularconcentrate pump opening 346. Concentrate pump opening is radiallydisposed from the axis of rotation 174 a concentrate pump openingdistance. In the exemplary arrangement the upper and lower concentratevane distances are less than the concentrate pump opening distance. Ofcourse it should be understood that this configuration is exemplary andin other arrangements other approaches may be used.

In the exemplary single use structure 314 the upper and lowerconcentrate chamber vanes 344, 340, and the upper and lower centratechamber vanes 326, 328 operate to stabilize and radially position theannular air/liquid interface 348 in the centrate pump chamber 330 andthe air/liquid interface 350 in the concentrate pump chamber 332. Asrepresented in FIG. 28 the air/liquid interface 348 is positionedradially intermediate along the radial length of the centrate chambervanes. This is radially inward from the centrate pump opening 330. Theradially extending centrate chamber vanes operate to provide centrifugalpumping force which maintains the annular air/liquid interface 348 at aradial location, both above and below the centrate centripetal pump,that is disposed radially inward of the centrate pump opening 330. Inexemplary arrangements the vanes further help to stabilize theair/liquid interface so that it maintains a coaxial circularconfiguration both above and below the centrate pump. Further inexemplary arrangements the radial position of the interface relative tothe axis of rotation can be controlled as later discussed so that thecentrate pump opening 330 is consistently maintained in the liquidcentrate and is not exposed to air.

The upper concentrate chamber vanes 344 and the lower concentratechamber vanes 340 work in a similar manner to the centrate chambervanes. The concentrate chamber vanes maintain the circular air/liquidinterface 350 in the concentrate pump chamber 332 at a radial distancethat is inward of the substantially annular concentrate pump opening346. This configuration assures that the concentrate pump opening isconsistently exposed to the concentrate and not to air. It shouldfurther be understood that although in the arrangement shown thecentrate centripetal pump and the concentrate centripetal pump are ofsubstantially the same size, and other arrangements the centripetalpumps may have different sizes. In such situations the radial distancefrom the axis of rotation that the centrate chamber vanes and theconcentrate chamber vanes extend may be different. Also the radialposition relative to the axis of rotation of the air/liquid interface inthe centrate pump chamber and the concentrate pump chamber may bedifferent. Numerous different vane configurations and arrangements maybe utilized depending on the particular relationships between thecomponents which make up the single use device and the particularmaterial that is processed via the single use structure.

FIG. 30 shows an upper portion of a further alternative single usestructure 352. The single use structure 352 is similar to single usestructure 304 except as otherwise discussed. Single use structure 352includes an air tube 354 that extends in coaxial surrounding relation ofthe concentrate discharge tube 220. The air tube 354 is in communicationwith openings 356 inside the single use structure. Openings 356 extendfrom the interior of the air tube to above the concentrate centripetalpump 216 in the concentrate pump chamber 332. In this exemplaryarrangement the seal 236 as schematically shown, operatively engages theair tube 354 to maintain the air tight engagement with the air tube aswell as the concentrate discharge tube, centrate discharge tube and thefeed tube. As can be appreciated the air tube may be utilized toselectively maintain the level of the air pressure in the air pocketwithin the single use structure. Such an arrangement may be utilized inconnection with systems like those previously discussed or in othersystems, in which an external supply of pressurized air is utilized toisolate the seal of the centrifuge structure from the material beingprocessed and to maintain the air/liquid interface at a desirablelocation. Of course it should be understood that this structure isexemplary and in other arrangements other approaches may be used.

FIG. 31 schematically shows a system 358 that may be used forcontinuously separating cell suspension into substantially cell freecentrate and concentrate. System 358 is similar to system 170 previouslydiscussed, except as otherwise mentioned herein. In the exemplaryarrangement system 358 operates using a single use structure similar tosingle use structure 352. The controller 274 of system 358 operates tocontrol the position of the air/liquid interface within the single usestructure to assure that the interface is maintained radially inwardrelative to the axis of rotation from each of the centrate pump openingand the concentrate pump opening.

In the exemplary arrangement a flow back pressure regulator 360 is influid connection with the centrate discharge line 262. In the exemplaryarrangement the flow back pressure regulator 360 is fluidly intermediateof the centrate discharge tube 212 and the centrate pump 266. Theexemplary system 358 includes a source of pressurized air schematicallyindicated 362. The source of pressurized air 362 is connected to a pilotpressure control valve 364. The control valve is in operative connectionwith the controller 274. Signals from the controller 274 causeselectively variable pressure in a pilot line 366. The pilot line 366 isin fluid connection with the back pressure regulator 360. The pressureapplied by the pilot pressure control valve 264 in the pilot line 366 isoperative to control the centrate flow and consequently the centrateflow back pressure that is applied by the flow back pressure regulator360.

In the exemplary arrangement a pressure control valve 368 is in fluidcommunication with the source of pressurized air 362. Control valve 368is also in operative connection with the controller 274. In thisexemplary arrangement the control valve 368 is controlled to selectivelyapply precise pressure to the air tube 354 and the air pocket within theupper portion of the single use structure 352.

In the exemplary arrangement the controller 274 operates in accordancewith stored executable instructions to control the operation of thesystem 358 in a manner like that previously discussed in connection withsystem 170. Further in the exemplary arrangement the controller 274operates to control the pilot pressure valve 364 to vary the backpressure that is applied to the centrate discharge tube 212 by the backpressure regulator 360. The controller 274 also operates to controlvalve 368. The controller operates to maintain and selectively vary thepressure applied in the air pocket at the top of the interior of thesingle use structure. The controller operates in accordance with itsprogramming to vary the back pressure of the centrate flow and/or theair pocket pressure to maintain the air/liquid interface of the airpocket at a radial distance from the axis of rotation that is inwardfrom the centrate pump opening 330 and the concentrate pump opening 346.This pressure variation in both the centrate flow back pressure and airpocket pressure, in combination with the action of the centrate chambervanes and concentrate chamber vanes in the exemplary arrangement,maintain the stability and radially outward extent of the air/liquidinterface so as to assure that introduction of air is minimized in thecentrate and concentrate outputs from the single use structure. Furtherthe ability to selectively vary the back pressure and flow of thecentrate can impact the level of cells and corresponding detectedoptical density of the discharged concentrate. Thus the controller mayoperate in accordance with its programming to selectively vary both theconcentrate flow rate, centrate back pressure and flow rate, internalair pocket pressure, the feed rate of cell suspension into the singleuse structure and perhaps other operating variables of thecentrifugation process, to maintain the centrate and concentrateproperties within the set limits and/or ranges stored in the at leastone data store associated with the controller. Further the exemplaryarrangement may enable separation of different types of materials andoperations at different flow rates while maintaining reliable control ofthe separation process. Of course while it should be understood that thecontrol of the position of the air/liquid interface is described inconnection with features of system 170, such control may also beutilized in systems of other types which include other or differenttypes of processing elements.

FIGS. 32-34 show further alternative single use structure 370. Exemplarysingle use structure 370 includes numerous features like those discussedin connection with previously described single use structures 178, 240and 250 for example. It should be understood that the additionalfeatures discussed herein that are used in connection with other singleuse structures may also be utilized in arrangements having the featuresand relationships shown in single use structure 370.

Single use structure 370 includes an upper disc shape portion 372. Theexemplary upper disc shape portion 372 includes therein a centratecentripetal pump chamber 374. Centrate centripetal pump 208 is housedwithin the centrate centripetal pump chamber 374. The centratecentripetal pump chamber has a centrate chamber volume within the upperdisc shape portion.

The centrate centripetal pump chamber is in fluid communication with theseparation chamber through at least one centrate channel 410. Thecentrate channel 410 is fluidly connected to at least one centratechannel inlet 412. The exemplary at least one centrate channel inlet 412is in fluid communication with the separation chamber in close proximityto but radially outward of the cylindrical wall of the cylindrical core.In the exemplary arrangement shown the at least one centrate channelinlet 412 is a single substantially annular inlet and the centratechannel is a single substantially annular channel.

The upper disc shape portion further includes a concentrate centripetalpump chamber 376. The exemplary concentrate centripetal pump chamber 376is a cylindrical chamber that is horizontally bounded by a verticallyextending circular bounding wall 378. The concentrate centripetal pumpchamber 376 has a concentrate chamber volume within the upper disc shapeportion. In the exemplary arrangement the centrate chamber volume withinthe upper disc shape portion is greater than the concentrate chambervolume for reasons that are later discussed.

The exemplary upper disc shaped portion is comprised of a upper piece394 and a lower piece 396. In the exemplary arrangement the upper pieceand lower piece are held together in releasable engagement. Of coursethis approach is exemplary and in other arrangements other approachesmay be used. The exemplary lower piece 396 in the operative position, isbounded at its upper side by an upper annular bounding surface 398. Theexemplary lower piece 396 is bounded at its lower side by a lowerannular bounding surface 400. The upper annular bounding surface 398includes a radially outward conical annular upper surface portion 402and a radially inward radially planar extending upper surface portion404. The lower annular bounding surface 398 includes a radially outwardconical annular lower surface portion 406 and a radially inward radiallyplanar extending lower surface portion 408. In the operative position ofthe upper piece 394 and the lower piece 396, the radially inwardradially planar horizontal extending lower surface 408 and the radiallyinward radially planar horizontal extending upper surface 404 extendparallel to one another. However in the operative position the conicalannular upper surface portion 402 and the conical annular lower surfaceportion are not in a parallel relationship for reasons that are laterdiscussed.

In the exemplary arrangement a substantially annular cell concentratechannel 380 extends between the upper piece 394 and the lower piece 396of the upper disc shape portion 372. The annular cell concentratechannel 380 extends radially inward from a substantially annular cellconcentrate channel inlet 382. The concentrate channel inlet is disposedfurther radially outward from the centrate inlet 412. The concentratechannel inlet 382 is positioned in fluid connection with an upper areaof the separation chamber 224 at a radially outer periphery adjacent tothe inside surface of the outer wall at which cell concentrate 384collects in an annular radially outward region 384 of the separationchamber during rotation of the device with a centrifuge bowl asrepresented in FIG. 34.

In the exemplary arrangement a substantially annular funnel channel 381extends upwardly and radially inward to the annular cell concentratechannel inlet 382. The exemplary lower piece 396 of the upper discshaped portion 372 in the operative position is bounded in theseparation chamber at a lower radially inward side by a substantiallyplanar radially extending surface 379. The exemplary radially extendingsurface 379 terminates radially outward at an annular edge 377. In theoperative position of the single use structure, the annular funnelchannel 381 extends upwardly from the annular edge 377. The exemplaryupper piece 394 of the exemplary annular disc shape portion 372 furtherincludes a substantially annular cell concentrate guide surface 383. Theannular cell concentrate guide surface 383 extends below the annularfunnel channel 381 and radially outwardly bounds the separation chamber224 at the axial level of the radially extending planar surface 379. Inthis exemplary arrangement the annular cell concentrate guide surface383 extends further radially outward with upward proximity to the funnelchannel.

In this exemplary arrangement the annular cell concentrate channel 380radially inwardly terminates in the concentrate centripetal pump chamber376 at a substantially annular cell concentrate outlet 386. In theexemplary arrangement the annular cell concentrate outlet 386 ispositioned so as to extend at the midpoint of the vertically extendingbounding wall 378. In this exemplary arrangement the concentratecentripetal pump includes a substantially annular concentratecentripetal pump inlet 388. The annular cell concentrate outlet of thechannel 380 is radially and axially aligned relation with theconcentrate centripetal pump inlet 388.

In the exemplary arrangement the annular cell concentrate channelincludes in axial cross-section a tapered portion 390 and a radiallyextending portion 392. The radially extending portion 392 extendsdirectly radially outward between the radially planar extending uppersurface portion 404 of the lower piece 396 and the radially planarextending lower surface portion 408 of the upper piece 394. Theexemplary radially extending portion 392 further extends directlyradially outward from the annular cell concentrate outlet 386. In theoperative position of the single use structure the horizontally andradially extending portion 392 of the annular cell concentrate channelis a constant channel height, wherein the height of the channel refersto the dimension of the channel transverse to the direction ofconcentrate flow in the respective area of the channel. As a result thehorizontally and radially extending portion is of a constantcross-sectional area throughout its entire length. In this exemplaryarrangement the horizontally and radially extending portion 392 isaxially and radially aligned and is of the same height in axialcross-section as the inlet of the concentrate centripetal pump.

The tapered portion 390 of the annular cell concentrate channel 380extends between the conical annular upper surface portion 402 of thelower piece and the conical annular lower surface portion 406 of theupper piece. The annular cell concentrate channel 380 is configured tohave a channel portion with a gradually continuously increasing channelheight (and cross-sectional channel area) from the cell concentratepassage inlet 382 to the position where the tapered portion fluidlyconnects with the radially extending portion 392. This configurationcauses the channel portion 390 to increase in cross-sectional areaperpendicular to the direction of concentrate flow within the channelportion, with increased proximity to the axis of rotation. The graduallycontinuously increasing cross-sectional area of the concentrate channelmeans that in the channel portion, the cross-sectional area of thechannel perpendicular to the direction of concentrate flow, increasessmoothly and without any discrete steps in locations in the channelportion where the channel cross-sectional area undergoes an immediatechange of more than 10% in the cross-sectional area.

The constantly increasing height of the channel with proximity to theaxis of rotation of the single use system within the tapered portion 390in the exemplary arrangement helps to maintain a suitably high fluidvelocity of the cell concentrate. In exemplary arrangements the annularcell concentrate channel has a configuration that avoids areas ofpressure drop to maintain a suitably high radially inward velocity ofthe constituents of the cell concentrate from the channel inlet 382 tothe passage outlet 386.

In the exemplary arrangement the annular inlet 382 to the annularchannel 380 is the portion of the channel that is the narrowest inheight in axial cross-section and is the smallest in cross-sectionalarea. At the annular inlet 382 the cells and the liquid in which thecells are suspended begin to flow radially inwardly. In this area of thesingle use structure the cells which are more dense than the liquid,experience a centrifugal acceleration force that is directed radiallyoutward due to centrifuge rotation. During operation of the exemplaryarrangement, an external concentrate pump such as concentrate pump 272previously discussed, is operated to maintain a flow rate that causes amean velocity of liquid flow radially inward at the annular channelinlet 382, that is above of a sedimentation velocity and a force actingon the cells directed radially outward that is caused by the centrifugalforce acting on the concentrate at the channel inlet. Further in someexemplary arrangements the upwardly tapered configuration of the taperedportion 390 causes the component of the sedimentation force opposing theflow of cells at the channel inlet and in the channel portion, to beless than that which would be opposing movement of the cells in adirectly radially inward channel at the same radial location.

In the exemplary arrangement the height of the annular tapered portionof the annular concentrate channel increases with decreased radialdistance from the axis of rotation of the single use structure. In theexemplary configuration of the channel in axial cross-section, thechannel height of the tapered portion 390 and therefore thecross-sectional area perpendicular to the direction of concentrate flow,gradually continuously increases with increasing proximity to(decreasing radial distance from) the axis of rotation of the single usestructure. The exemplary configuration in which the height of thechannel gradually continuously increases as a function of the decreasingradial distance from the axis enables the cells in the cell concentrateto continuously move throughout the concentrate channel at a suitablyhigh velocity radially inward with the liquid in which the cells aresuspended. A suitably radially inward velocity is enabled to bemaintained throughout the radially inward travel of the cell concentratefrom the channel inlet 382 despite the increasing channel height, due tothe decreasing radially outward directed centrifugal acceleration forcethat acts on the cells with correspondingly decreasing radial distancefrom the axis of rotation. Thus in the exemplary arrangement the cellconcentrate maintains a suitably high radially inward velocity in thechannel portion 390 throughout the channel 380 as the cell concentratemoves radially inward from the annular inlet 382 toward the cellconcentrate outlet 386 and into and through the concentrate centripetalpump chamber 376.

It should be understood that while in the exemplary arrangement shown inFIGS. 32-34 the channel portion that includes the gradually continuouslyincreasing cross-section area begins at the channel inlet, in otherarrangements other approaches and configurations may be used. Forexample, in some alternative arrangements the channel portion havingthis configuration may be disposed in other locations. Such location maydepend on the particular configuration of the concentrate channel andthe requirement in a particular portion of the channel to have theconcentrate achieve a sufficiently high flow velocity to help move theconcentrate and the cells therein in a desired manner that overcomessedimentation or other forces opposing the desired flow. Further itshould be understood that while in this exemplary arrangement there isonly a single annular concentrate channel portion with a graduallycontinuously increasing cross-sectional area, other arrangements mayinclude other channels such as multiple concentrate channels. It shouldbe understood that the arrangement shown in FIGS. 32-34 is exemplary andthat other arrangements may be used.

In the exemplary arrangement the concentrate discharge tube 220 is inoperative fluid connection with the external concentrate pump aspreviously discussed. In exemplary arrangements the concentrate pump mayoperate in a system similar to system 170 previously described or othersystem responsive to control circuitry to provide outlet flow of cellconcentrate while maintaining a suitable back pressure in theconcentrate discharge tube. Of course it should be understood thatnumerous other types of components may be included in the system inwhich the single use structure 370 is operated to achieve theoperational capabilities described herein.

In operation of the exemplary system the single use structure 370 isrotated in operative connection with a centrifuge bowl to separate cellsuspension in the interior area of the structure. The cell suspension isseparated into cell centrate which is substantially depleted of cells,and cell concentrate that is enriched in cells in a manner like thatpreviously discussed. In the exemplary arrangement centrifugal actioncreates an annular cell concentrate region 384 at the upper, radiallyouter periphery of the separation chamber. The exemplary annular cellconcentrate region is maintained in fluid connection with the annularchannel inlet 382 as well as in contacting relation with thesubstantially annular cell concentrate guide surface and the annularfunnel channel along which the cell concentrate moves toward the channelinlet 382.

In some exemplary arrangements the configuration of the annular cellconcentrate guide surface 383 which bounds the radially outer peripheryof the separation chamber adjacent to radially extending surface 379 ofthe upper disc shaped portion may operate to urge cell concentrateupwardly into the annular funnel channel 381. This may result because ofthe configuration of the guide surface which extends further radiallyoutward with upward proximity to the final passage. The cell concentratewhich is urged radially outwardly against the annular cell concentrateguide surface 383 by the centrifugal force produced by rotation of thecentrifuge, may be moved in engagement with the guide surface into theannular funnel channel, which guides the cell concentrate to move upwardand radially inward to the annular cell concentrate inlet. As the cellconcentrate is guided radially upwardly toward the channel inlet 382 bythe annular converging surfaces that an axial cross-section bound theannular funnel channel, the radially inward velocity of the liquidcomponent of the cell concentrate increases with the decrease in area ofthe funnel channel. As previously discussed the exemplary configurationhas the smallest height dimension, (and the smallest cross-sectionalarea) which is configured to produce the highest fluid velocity of theliquid phase of the cell concentrate, at the annular channel inlet 382.

In the exemplary arrangement and its method of operation, the externalconcentrate pump is operative to produce a flow that causes the cellconcentrate in the annular cell concentrate channel 380 to movecontinuously from the cell concentrate annular inlet 382 to the cellconcentrate annular outlet 386 at a flow rate that produces a meanvelocity of the liquid phase of the cell concentrate radially inwardthat is higher than a settling velocity of the cells. In the exemplaryarrangement the achievement of such a consistently high mean velocityfor the liquid phase in the cell concentrate across the height of thepassage and throughout the entire radial length of the passage helps toassure that the cell concentrate and the cells therein suitably movethrough the annular cell concentrate channel. Further in the exemplaryarrangement the gradually continuously increasing cross-section of thetapered portion 390 of the channel, the constant height of the radiallyextending portion 392, and the generally constant relatively smallcross-sectional area throughout the length of the entire annular cellconcentrate channel, avoids areas of significant pressure drop along thelength of the channel so that the velocity of the liquid phase and thecells are maintained continuously sufficiently high throughout thepassage.

Further in operation of the exemplary arrangement the cell concentrateentering the concentrate centripetal pump chamber 376 is caused to moveat a velocity and flow rate sufficiently high to assure that the liquidand cell phases of the cell concentrate pass radially inwardly throughthe inlet of the concentrate centripetal pump. This result isfacilitated in the exemplary arrangement by the volume and configurationof the concentrate centripetal pump chamber as well as the configurationof the channel outlet 386 relative to the centripetal pump inlet 388 ofthe centripetal pump 216.

These features of the exemplary arrangement facilitate the radiallyinward flow of cell concentrate in the exemplary single use structureand achieve beneficial operation of the single use structure and theassociated system. Of course it should be understood that these featuresand configurations are exemplary, and the principles described hereinmay be utilized in connection with other configurations and other singleuse or multiple use structures to achieve desirable performanceproperties and cell separation in other centrifugation processes.

FIGS. 35 through 38 show a further alternative arrangement of a singleuse structure 414. This exemplary alternative single use structureincludes many features of the previously described arrangements. Theexemplary single use structure includes an upper disc shape portion 416.An outer wall 418 is configured to be in operative connection with thecentrifuge bowl within which the single use structure 414 is configuredto be positioned. The structure includes a lower portion 420 of the wall418. The exemplary single use structure as shown in FIG. 36 has aninternal area with a truncated cone shape and a smaller inside radiusadjacent to the lower portion 420.

Similar to the previously described arrangements, single use structure414 includes a cylindrical core 422. Cylindrical core 422 extendsaxially between the upper and lower portions of the internal area of thestructure. The core includes a cylindrical outer bounding wall 424. Itshould be understood that although the core 422 is shown as a solidstructure in FIG. 36, in other arrangements a hollow core structure maybe used. In the exemplary arrangement the cylindrical core 422 extendsin the interior area between the bottom of the upper disc shaped portionand a plurality of upwardly directed angularly spaced vanes 426. Thevanes 426 include fluid channels therebetween that extend upwardly fromthe inside of the wall bounding a lower portion of the interior area ofthe single use structure.

In the exemplary arrangement the single use structure 414 is configuredto be rotatable in a centrifuge bowl about an axis 428. The single usestructure further includes in the operative position, a verticallyextending feed tube 430 which is configured to receive cell culturematerial into the interior area of the structure. The exemplary feedtube 430 extends downward to a tube opening 432 in the lower portion ofthe single use structure into an area in which incoming material that isto be separated into cell centrate and cell concentrate is introduced.In the exemplary arrangement shown the feed tube 430 extends axiallythrough a cylindrical opening 434 in the core.

The exemplary single use structure further includes in the operativeposition, a vertically extending centrate discharge tube 436. Thevertically extending centrate discharge tube 436 is fluidly connected toa centrate centripetal pump 438. The centrate centripetal pump ispositioned in a centrate centripetal pump chamber 440 that is positionedin the upper disc shape portion 416. The centrate centripetal pumpchamber 440 is in fluid connection with the separation chamber 442 thatextends radially between the outer wall of the core 422 and the wallthat bounds the interior area of the single use structure. The centratecentripetal pump chamber is fluidly connected to the separation chamber442 through at least one centrate channel inlet 444 and at least onecentrate channel 446. In the exemplary arrangement the at least onecentrate channel inlet 444 is positioned in the separation chamberradially outward of the cylindrical wall bounding the core 422, but inclose radial proximity thereto. In the exemplary arrangement thecentrate channel inlets have an arcuate shape. Further in the operativeposition of exemplary arrangement the centrate centripetal pump chamber440 includes horizontally extending upper and lower centrate pumpchamber surfaces which may include upper and lower centrate chambervanes such as vanes 326 and 328 previously discussed.

The exemplary single use structure 414 further includes in the operativeposition, a vertically extending concentrate discharge tube 448. As inthe other described arrangements the concentrate discharge tube 448, thecentrate discharge tube 436 and the feed tube 430 are coaxially arrangedon the single use structure. The concentrate discharge tube 448 is influid connection with a concentrate centripetal pump 450. Theconcentrate centripetal pump 450 is positioned in a concentratecentripetal pump chamber 452 within the upper disc shape portion 416. Inthe exemplary arrangement the concentrate centripetal pump chamber isbounded by respective upper and lower concentrate centripetal pumpchamber surfaces each of which may include radially extending chambervanes similar to those previously discussed.

In this exemplary arrangement the concentrate centripetal pump chamberis in fluid connection with the separation chamber through a pluralityof radially extending concentrate channels 454. In the exemplaryarrangement each of the concentrate channels extend within the upperdisc shaped portion and are angularly spaced from each of the otherchannels. The exemplary upper disc shape portion 416 is comprised of anupper piece 456 and a lower piece 458. The exemplary upper disc shapedportion further includes a bottom piece 460. In the exemplaryarrangement in the operative condition, each of the upper piece 456, thelower piece 458 and the bottom fees 460 are in sandwiched engagedrelation. In the operative position each of the plurality of concentratechannels is bounded by the at least one lower facing surface of theupper piece 456 and at least one upper facing surface of the lower piece458.

As shown in FIG. 36 each of the plurality of concentrate channels 454includes a concentrate channel inlet 462. In the exemplary arrangementthe concentrate channel inlet has the smallest cross-sectional area in adirection perpendicular to the direction of concentrate flow, throughoutthe respective concentrate channel. Each concentrate channel inlet 462is fluidly connected to an outer periphery of the separation chamberthrough a vertical opening 464 that extends in the upper disc shapeportion. In the exemplary arrangement each concentrate channel 454 isfluidly connected to the separation chamber through a respectivevertical opening 464 that extends through the bottom piece 460 and isbetween and bounded by the upper piece 456 and the lower piece 458. Inthe exemplary arrangement each of the respective vertical openings 464include arcuate elongated slots in the bottom piece 460. Of course itshould be understood that this configuration is exemplary and otherarrangements other approaches may be used.

In the exemplary arrangement each concentrate channel has a generallyconstant cross-sectional width from the channel inlet 462 to therespective opening from the channel into the concentrate centripetalpump chamber. Each of the concentrate channels includes a channelportion that gradually continuously increases in cross-sectional areaperpendicular to the direction of concentrate flow within the respectiveconcentrate channel portion. The cross-sectional area increases withcorresponding increased proximity of the location in the channel portionto the axis of the single use structure. In the exemplary arrangementthe plurality of concentrate channels are each configured such that in atapered portion 468 the cross-sectional area perpendicular to thedirection of concentrate flow gradually and continuously increases as aresult of the varied height of the channel in the tapered portion. Theheight of each channel increases with increasing proximity to the axisof rotation. Of course it should be understood that this arrangement isexemplary and in other arrangements other approaches may be used.

In the exemplary arrangement each channel portion which has thegradually continuously increasing cross-sectional area configurationbegins at the respective concentrate channel inlet 462 and continuesthrough the tapered portion 468 which extends upward and radially inwardtherefrom. Each tapered portion 468 is fluidly connected to ahorizontally and radially extending portion 470 of the respectiveconcentrate channel 454. In the exemplary arrangement each horizontallyand radially extending portion of the respective concentrate channelextends from the tapered portion 468 to the concentrate centripetal pumpchamber 450. In the exemplary arrangement the horizontally and radiallyextending portions of the concentrate channels are of constantcross-sectional area in the direction perpendicular to concentrate flow,from the tapered portion radially inward to the concentrate centripetalpump chamber. However it should be understood that this arrangement isexemplary and in other arrangements other approaches may be used.

In the operation of the exemplary single use structure 414, the upperdisc shape portion 416, the wall 418 and the core rotate in operativeconnection with the centrifuge bowl. The feed tube 430, centratedischarge tube 436 and concentrate discharge tube 448, along with theconcentrate centripetal pump 450 and the centrate centripetal pump 438remain stationary. In the exemplary arrangement cell culture material isseparated by the rotationally produced centrifugal force, into cellcentrate and cell concentrate in the separation chamber 442. The cellconcentrate accumulates in the upper and radially outer region of theseparation chamber 442 while the substantially cell free centrateaccumulates in the area of the separation chamber in proximity to thecylindrical outer wall of the core.

The centrate passes into the centrate centripetal pump chamber throughthe plurality of centrate channel inlets 444 and moves out from thecentripetal pump chamber through the centrate centripetal pump 438 andcentrate discharge tube. An external concentrate pump like thosepreviously discussed, is in operative connection with the concentratedischarge tube and causes concentrate flow from the separation chamberof the single use structure. This concentrate flow causes the cellconcentrate to pass upwardly through each vertical opening 464 and toeach respective concentrate channel inlet 462 at which the relativelysmall cross-sectional area of the concentrate channel inlet causes thecell concentrate to have a high flow velocity. The high flow velocity ofthe liquid and cells of the cell concentrate operates to impart a forceto the cells included in the cell concentrate that urges the cells tomove in the upward and radially inward tapered portion 468 by overcomingthe radially outward directed forces that are acting on the cells in amanner like that discussed in connection with the prior arrangement.

The upwardly and radially inward extending tapered portion graduallycontinuously increases in cross-sectional area perpendicular to thedirection of the concentrate flow. This gradually and continuouslyincreasing cross-sectional area maintains the flow velocity of theconcentrate sufficiently high at each radial location throughout thechannel portion to assure that the cell concentrate continues to movetoward the concentrate chamber at a suitably high velocity despite theradially outward acting forces in each location in the channel portion.The cell concentrate in the exemplary arrangement leaves the taperedportion of the concentrate channel and passes through the horizontallyand radially extending portions of each respective channel to reach theconcentrate centripetal pump chamber 452 through which the cellconcentrate maintains a suitably high velocity. As a result theexemplary arrangement is enabled to provide flow characteristics for thecell concentrate which facilitate cell concentrate flow within thesingle use structure and aid in the process of cell separation. Ofcourse as can be appreciated, the configuration of single use structure414 is exemplary and in other arrangements other configurations may beused.

In some exemplary arrangements the upper piece, lower piece and bottompiece of the upper disc shaped portion 416 may be releasably engageable.This may be done to facilitate manufacture as well as to enableinspection, cleaning or other purposes. In other exemplary arrangementsthe pieces may be permanently engaged. In still other exemplaryarrangements structures similar to those described may be formed fromother components which provide the useful characteristics andcapabilities that have been discussed herein. Further it should beunderstood that the configuration of single use structure 414 isexemplary and the useful principles and structures described herein maybe used in other separator structure arrangements.

Thus the new centrifuge system and method of the exemplary arrangementsachieves at least some of the above stated objectives, eliminatesdifficulties encountered in the use of prior devices and systems, solvesproblems and attains the desirable results described herein.

In the foregoing description certain terms have been used for brevity,clarity and understanding, however, no unnecessary limitations are to beimplied there from because such terms are for descriptive purposes andare intended to be broadly construed. Moreover, the descriptions andillustrations herein are by way of examples and the inventive featuresare not limited to the exact details shown and described.

It should be understood that the features and/or relationshipsassociated with one exemplary arrangement can be combined with thefeatures and/or relationships from another exemplary arrangement. Thatis, various features and/or relationships from various arrangements canbe combined in further arrangements. The inventive scope of thedisclosure is not limited solely to the exemplary arrangements that havebeen shown and described herein.

In the following claims any feature described as a means for performinga function shall be construed as encompassing any means known to thoseskilled in the field as capable of performing the recited function, andshall not be limited to the structures shown herein or mere equivalentsthereof.

Having described the features, discoveries and principles of the new anduseful features, the manner in which they are constructed, utilized andoperated, and the advantages and useful results attained, the new anduseful structures, devices, elements, arrangements, parts, combinations,systems, equipment, operations, methods and relationships are set forthin the appended claims.

We claim:
 1. Apparatus comprising: a structure configured to bereleasably housed in a rotatable centrifuge bowl, wherein the structureis positionable within the bowl and is operative to separate within aninterior area of the structure, cells in a cell culture material intocell concentrate and cell centrate, wherein the structure in anoperative position includes an upper disc shape portion, a lowerportion, a cylindrical core vertically intermediate of the upper discshape portion and the lower portion, a separation chamber disposedradially outward from and in surrounding relation of the core, an outerwall configured to be in operative engagement with the bowl, wherein theouter wall extends in fluid tight relation with the upper disc shapeportion and bounds the separation chamber, extends in surroundingrelation of the core and the separation chamber, and has an internaltruncated cone shape with a smaller inside radius adjacent the lowerportion than adjacent the upper disc shape portion, a verticallyextending feed tube, a vertically extending centrate discharge tube, avertically extending concentrate discharge tube, wherein the upper discshape portion and the outer wall are rotatable in operative engagementwith the bowl about a vertical axis, a centrate centripetal pump,wherein the centrate centripetal pump is axially aligned with the core,is disposed coaxially about the feed tube, and is in fluid communicationwith the centrate discharge tube, wherein the centrate centripetal pumpis positioned in a centrate centripetal pump chamber within the upperdisc shape portion, wherein the centrate centripetal pump chamber is influid communication with the separation chamber through at least onecentrate channel that extends in the upper disc shape portion, whereineach centrate channel extends fluidly between a respective centratechannel inlet that is positioned radially outward of the core, and thecentrate centripetal pump chamber, a concentrate centripetal pump,wherein the concentrate centripetal pump is axially aligned with thecore, is disposed coaxially about the feed tube, is positionedvertically above the centrate centripetal pump and is in fluidcommunication with the concentrate discharge tube, wherein theconcentrate centripetal pump is positioned in a concentrate centripetalpump chamber within the upper disc shape portion, wherein theconcentrate centripetal pump chamber is in fluid communication with theseparation chamber through at least one radially extending concentratechannel that extends in the upper disc shape portion, wherein each ofthe at least one radially extending concentrate channel extends radiallybetween a respective concentrate channel inlet that is disposed radiallyoutward of every centrate inlet, wherein during rotation of the bowl theupper disc shape portion and the outer wall rotate relative to each ofthe feed tube, the centrate discharge tube, the concentrate dischargetube, the centrate centripetal pump and the concentrate centripetalpump, wherein each concentrate channel includes a channel portionintermediate of the respective concentrate channel inlet and theconcentrate centripetal pump chamber that gradually continuouslyincreases in cross-sectional area perpendicular to a direction ofconcentrate flow within the respective concentrate channel portion area,with corresponding increased radial proximity to the axis.
 2. Theapparatus according to claim 1 wherein the channel portion of eachconcentrate channel begins at the respective concentrate channel inletand extends radially inward.
 3. The apparatus according to claim 1wherein the channel portion of each concentrate channel begins at therespective concentrate channel inlet and extends both radially inwardand upward from the concentrate channel inlet.
 4. The apparatusaccording to claim 1 wherein the channel portion of each concentratechannel begins at the respective concentrate channel inlet and extendsboth radially inward and upward from the concentrate channel inlet,wherein each concentrate channel further includes a horizontally andradially extending portion, wherein the horizontally and radiallyextending portion extends fluidly intermediate of the channel portionand the concentrate centripetal pump chamber.
 5. The apparatus accordingto claim 1 wherein the channel portion of each concentrate channelbegins at the respective concentrate channel inlet and extends bothradially inward and upward from the concentrate channel inlet, whereineach concentrate channel further includes a horizontally and radiallyextending portion, wherein the horizontally and radially extendingportion extends fluidly intermediate of the channel portion and theconcentrate centripetal pump chamber wherein the horizontally andradially extending portion of each concentrate channel terminatesradially inward at a respective cell concentrate channel outlet in theconcentrate centripetal pump chamber, wherein the horizontally andradially extending portion of each concentrate channel is of a constantcross-sectional area throughout its entire length.
 6. The apparatusaccording to claim 1 wherein the channel portion of each concentratechannel begins at the respective concentrate channel inlet and extendsboth radially inward and upward from the concentrate channel inlet,wherein each concentrate channel further includes a respectivehorizontally and radially extending portion, wherein the horizontallyand radially extending portion extends radially outward from theconcentrate centripetal pump chamber.
 7. The apparatus according toclaim 1 wherein the channel portion of each concentrate channel beginsat the respective concentrate channel inlet and extends both radiallyinward and upward from the concentrate channel inlet, wherein eachconcentrate channel further includes a respective horizontally andradially extending portion, wherein the horizontally and radiallyextending portion extends outward from the concentrate centripetal pumpchamber, wherein the channel portion terminates radially inwardly at thehorizontally and radially extending portion, wherein the horizontallyand radially extending portion of each respective concentrate channel isof a constant cross-sectional area throughout its entire length.
 8. Theapparatus according to claim 1 wherein the channel portion of eachconcentrate channel begins at the respective concentrate channel inletand extends both radially inward and upward from the concentrate channelinlet, wherein each concentrate channel further includes a respectivehorizontally and radially extending portion, wherein the horizontallyand radially extending portion extends outward from a respective cellconcentrate channel outlet to the concentrate centripetal pump chamber,wherein the concentrate centripetal pump includes a concentratecentripetal pump inlet, wherein each cell concentrate channel outlet isaxially and radially aligned with the concentrate centripetal pumpinlet. wherein each channel portion terminates radially inwardly at arespective horizontally and radially extending portion, wherein thehorizontally and radially extending portion of each respectiveconcentrate channel is of a constant cross-sectional area throughout itsentire length.
 9. The apparatus according to claim 1 wherein the upperdisc shape portion comprises an upper piece and the lower piece inengaged relation, wherein each concentrate channel is bounded by atleast one lower surface of the upper piece and at least one uppersurface of the lower piece.
 10. The apparatus according to claim 1wherein the at least one radially extending concentrate channelcomprises a single substantially annular concentrate channel.
 11. Theapparatus according to claim 1 wherein the at least one radiallyextending concentrate channel comprises a plurality of separate,angularly spaced concentrate channels.
 12. The apparatus according toclaim 1 wherein the at least one radially extending concentrate channelcomprises a single substantially annular concentrate channel, whereinthe channel portion of the concentrate channel begins at a substantiallyannular concentrate channel inlet and extends both radially inward andupward from the concentrate channel inlet.
 13. The apparatus accordingto claim 1 wherein the at least one radially extending concentratechannel comprises a single substantially annular concentrate channel,wherein the channel portion of the concentrate channel begins at asubstantially annular concentrate channel inlet and extends bothradially inward and upward from the concentrate channel inlet. whereinthe concentrate channel further includes substantially annularhorizontally and radially extending portion, wherein the horizontallyand radially extending portion extends outward from a substantiallyannular cell concentrate channel outlet to the concentrate centripetalpump chamber, wherein channel portion terminates radially inwardly atthe horizontally and radially extending portion.
 14. The apparatusaccording to claim 1 wherein the at least one radially extendingconcentrate channel comprises a single substantially annular concentratechannel, wherein the channel portion of the concentrate channel beginsat a substantially annular concentrate channel inlet and extends bothradially inward and upward from the concentrate channel inlet, whereinthe upper disc shape portion includes a substantially annular funnelchannel, wherein the annular funnel channel extends upward and radiallyinward to the annular concentrate channel inlet.
 15. The apparatusaccording to claim 1 wherein the at least one radially extendingconcentrate channel comprises a single substantially annular concentratechannel, wherein the channel portion of the concentrate channel beginsat a substantially annular concentrate channel inlet and extends bothradially inward and upward from the concentrate channel inlet, whereinthe upper disc shape portion includes a substantially annular funnelchannel, wherein the annular funnel channel extends upward and radiallyinward to the annular concentrate channel inlet, wherein the upper discshape portion includes a substantially annular cell concentrate guidesurface, wherein the annular cell concentrate guide surface extendsbelow the annular funnel channel and radially outwardly bounds theseparation chamber, wherein the annular cell concentrate guide surfaceextends further radially outward with upward proximity to the annularfunnel channel.
 16. The apparatus according to claim 1 wherein the atleast one radially extending concentrate channel comprises a singlesubstantially annular concentrate channel, wherein the channel portionof the concentrate channel begins at a substantially annular concentratechannel inlet and extends both radially inward and upward from theconcentrate channel inlet, wherein the upper disc shape portion includesa substantially annular funnel channel, wherein the annular funnelchannel extends upward and radially inward to the annular concentratechannel inlet, wherein the upper disc shape portion includes asubstantially annular cell concentrate guide surface, wherein theannular cell concentrate guide surface extends below the annular funnelchannel and radially outwardly bounds the separation chamber, whereinthe annular cell concentrate guide surface extends further radiallyoutward with upward proximity to the annular funnel channel, wherein theupper disc shape portion is bounded at a lower side in the separationchamber by a radially extending surface, wherein the radially extendingsurface terminates radially outwardly at a substantially annular edge,wherein the annular edge is axially above the radially outward extendingannular cell concentrate guide surface, and wherein the annular funnelchannel extends upwardly from the annular edge.
 17. The apparatusaccording to claim 1 wherein the at least one radially extendingconcentrate channel comprises a plurality of separate, angularly spacedconcentrate channels, wherein the channel portion of each respectiveconcentrate channel begins at the respective concentrate channel inletand extends both radially inward and upward from the concentrate channelinlet, and has a constant cross-sectional width perpendicular to thedirection of concentrate flow and a vertical height that varies withradial distance from the axis.
 18. The apparatus according to claim 1wherein the at least one radially extending concentrate channelcomprises a plurality of separate, angularly spaced concentratechannels, wherein the channel portion of each respective concentratechannel begins at the respective concentrate channel inlet and extendsboth radially inward and upward from the concentrate channel inlet, andhas a constant cross-sectional width perpendicular to the direction ofconcentrate flow, and a vertical height that varies with radial distancefrom the axis. wherein the upper disc shape portion includes a pluralityof angularly spaced vertical openings, wherein a respective verticalopening extends between a radially outer periphery of the separationchamber and a respective channel inlet.
 19. The apparatus according toclaim 1 wherein the at least one radially extending concentrate channelcomprises a plurality of separate, angularly spaced concentratechannels, wherein the channel portion of each respective concentratechannel begins at the respective concentrate channel inlet and extendsboth radially inward and upward from the concentrate channel inlet, andhas a constant cross-sectional width perpendicular to the direction ofconcentrate flow and a vertical height that varies with radial distancefrom the axis, wherein the upper disc shape portion comprises an engagedupper piece and lower piece, wherein each concentrate channel is boundedby a respective surface of each of the upper piece and the lower piece.20. The apparatus according to claim 1 wherein the structure comprises asingle use structure.
 21. Apparatus comprising: a structure configuredto be releasably housed in a rotatable centrifuge bowl, wherein thestructure is positionable within the bowl and is operative to separatewithin an interior area of the structure, cells in a cell culturematerial into cell concentrate and cell centrate, wherein the structurein an operative position includes an upper disc shape portion, acylindrical core that extends vertically below the upper disc shapeportion, an outer wall configured to be in operative engagement with thebowl, wherein the outer wall extends in fluid tight engagement with theupper disc shape portion, extends in surrounding relation of the core,has a truncated cone shape with a smaller inside radius at an end of thestructure disposed vertically away from the upper disc shape portion,bounds a separation chamber within the structure that extends insurrounding relation of the core and radially intermediate of the coreand the outer wall, a vertically extending cell culture material feedtube, a vertically extending centrate discharge tube, a verticallyextending concentrate discharge tube wherein the upper disc shapeportion and the outer wall are rotatable in operative engagement withthe bowl about a vertical axis, wherein the feed tube, centratedischarge tube and the concentrate discharge tube are coaxial with thevertical axis, wherein the upper disc shape portion includes a centratecentripetal pump chamber, wherein the centrate centripetal pump chamberis in fluid communication with the separation chamber through at leastone centrate opening, a concentrate centripetal pump chamber, whereinthe concentrate centripetal pump chamber is in fluid communication withthe separation chamber through at least one concentrate channel, whereinthe at least one concentrate channel includes a concentrate channelinlet, wherein the concentrate channel inlet is disposed radiallyoutward from the at least one centrate opening, extends radially andfluidly between the at least one concentrate inlet and the concentratecentripetal pump chamber, a centrate centripetal pump, wherein thecentrate centripetal pump is disposed coaxially about the feed tube inthe centrate centripetal pump chamber and is in fluid communication withthe centrate discharge tube, a concentrate centripetal pump, wherein theconcentrate centripetal pump is disposed coaxially about the feed tubein the concentrate centripetal pump chamber, is positioned verticallyabove the centrate centripetal pump and is in fluid communication withthe concentrate discharge tube, wherein during rotation of the bowl theupper disc shape portion and the outer wall rotate relative to each ofthe feed tube, the centrate discharge tube, the concentrate dischargetube, the centrate centripetal pump and the concentrate centripetalpump, wherein each concentrate channel includes a channel portion thatextends intermediate of the respective concentrate channel inlet and theconcentrate centripetal pump chamber, wherein the channel portiongradually and continuously increases in cross-sectional areaperpendicular to a direction of concentrate flow within the respectiveconcentrate channel portion with corresponding increased radialproximity to the axis.
 22. The apparatus according to claim 21 whereineach respective concentrate channel portion begins at the respectiveconcentrate channel inlet of the respective concentrate channel andextends radially inward and upward from the respective channel inlet.23. The apparatus according to claim 22 wherein the at least one channelcomprises a single substantially annular concentrate channel.
 24. Theapparatus according to claim 22 wherein the at least one channelcomprises a plurality of separated angularly spaced concentratechannels.